Linear functions are everywhere around you - from calculating your... Show more
Mathematics
Irish
EnglishSign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
4
•
Updated May 8, 2026
•
Exploring Linear Functions: Graphing and Relationships
1 / 7
Understanding Linear Functions
Think of a linear function as a mathematical rule that always creates a straight line when you plot it on a graph. The clue's in the name - "linear" comes from "line"! These functions show how two things are connected in a steady, predictable way.
The magic formula you need to master is y = mx + c. This might look intimidating at first, but it's actually your best friend for understanding how lines work. Every linear function can be written this way.
You'll also need to get comfortable with some key vocabulary. A function is simply a rule that takes one number (x) and gives you exactly one answer (y). Variables are the letters (like x and y) that can change, while constants are the numbers that stay the same. Coordinates are pairs of numbers like (3, 4) that tell you exactly where to put a point on your graph.
Quick Tip: Remember coordinates as "across the hall, then up the stairs" - go across the x-axis first, then up or down the y-axis!
The Two Most Important Parts
Every linear equation has two crucial components that control how your line looks. The slope (m) tells you how steep your line is - it's like the angle of a ramp. If m = 2, your line goes up 2 units for every 1 unit it goes across. Pretty straightforward!
The y-intercept (c) is where your line crosses the vertical y-axis. If c = 3, you know your line will pass through the point (0, 3) every single time. This gives you an instant starting point for drawing your graph.
Understanding these two parts means you can look at any equation like y = 2x + 1 and immediately know: "This line has a slope of 2 and crosses the y-axis at 1." You're already halfway to drawing the perfect graph!
Remember: Positive slopes go uphill from left to right, negative slopes go downhill. It's that simple!
Creating Your Table of Values
Here's where the real work begins, but don't worry - it's just following a recipe. Start with your linear function in the form y = mx + c. Let's use y = 2x + 1 as our example.
Your mission is to find at least three points that lie on this line. Pick simple x-values like -1, 0, 1, and 2 to make your calculations easy. Nobody wants to work with horrible fractions when they don't have to!
Now substitute each x-value into your equation. When x = 0: y = 2(0) + 1 = 1. When x = 1: y = 2(1) + 1 = 3. When x = 2: y = 2(2) + 1 = 5. See the pattern? Your y-values are increasing by 2 each time because your slope is 2.
Pro Tip: If your three points don't line up perfectly when you plot them, check your maths - one of your calculations has gone wrong!
Plotting and Drawing Your Graph
Time to bring your calculations to life! Draw your axes with a ruler , label them clearly, and don't forget those arrows on the ends. Your Cartesian plane should look professional.
Plot each coordinate pair from your table carefully. For (-1, -1), go 1 unit left and 1 unit down from the origin. For (0, 1), stay on the y-axis and go 1 unit up. For (1, 3), go 1 unit right and 3 units up.
Once all your points are marked, use your ruler to draw one straight line through them all. Extend the line beyond your points with arrows to show it continues forever. Label your line with its equation - teachers love to see this attention to detail.
Golden Rule: Three points minimum! Two points make a line, but the third point proves you haven't made any mistakes.
Worked Example: Positive Slope
Let's tackle y = x + 3 step by step. This linear function has a slope of 1 (remember, x means 1x) and a y-intercept of 3. So you know it goes up gently and crosses the y-axis at 3.
Choose x = -2, 0, and 2 for easy calculations. When x = -2: y = (-2) + 3 = 1. When x = 0: y = (0) + 3 = 3. When x = 2: y = (2) + 3 = 5. Your coordinates are (-2, 1), (0, 3), and (2, 5).
Plot these points and connect them with a straight line. Notice how the line goes up from left to right? That's because your slope is positive. The line crosses the y-axis exactly where you predicted - at y = 3.
Check Yourself: Does your line pass through (0, 3)? If not, something's gone wrong with your plotting!
Worked Example: Negative Slope
Now let's try y = -2x + 4, which has a negative slope of -2. This means your line will slope downwards from left to right - quite dramatically because -2 is fairly steep. The y-intercept is 4.
Using x = 0, 1, and 2: When x = 0: y = -2(0) + 4 = 4. When x = 1: y = -2(1) + 4 = 2. When x = 2: y = -2(2) + 4 = 0. Your coordinates are (0, 4), (1, 2), and (2, 0).
Plot these points and draw your line. See how it slopes downward? For every step right, the line drops 2 steps down. This linear function creates a perfect straight line that behaves exactly as the equation predicts.
Pattern Spot: Notice how y decreases by 2 each time x increases by 1? That's your slope of -2 in action!
Exam Success Tips
Master these essentials and you'll smash any linear functions question. Always remember: y = mx + c where m is slope and c is y-intercept. Positive slopes go uphill, negative slopes go downhill. Simple!
Your foolproof method: create a table, pick 3-4 simple x-values, calculate y-values, plot coordinates, and join with a ruler. Label everything clearly - your axes, your line, and its equation. Teachers notice these details.
The y-intercept gives you a brilliant quick check. For y = 2x + 1, your line must cross the y-axis at 1. If it doesn't, you've made an error somewhere. Use this as your safety net in exams.
Exam Hack: If you're running short on time, just find the y-intercept and one other point. Two points are enough to draw the line, though three is always safer!
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Most popular content in Mathematics
Most popular content
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.6/5
App Store
4.7/5
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Exploring Linear Functions: Graphing and Relationships
Linear functions are everywhere around you - from calculating your mobile phone bill to tracking how fast you're cycling. They create perfect straight lines when graphed and follow predictable patterns that make maths much easier once you get the hang... Show more
Understanding Linear Functions
Think of a linear function as a mathematical rule that always creates a straight line when you plot it on a graph. The clue's in the name - "linear" comes from "line"! These functions show how two things are connected in a steady, predictable way.
The magic formula you need to master is y = mx + c. This might look intimidating at first, but it's actually your best friend for understanding how lines work. Every linear function can be written this way.
You'll also need to get comfortable with some key vocabulary. A function is simply a rule that takes one number (x) and gives you exactly one answer (y). Variables are the letters (like x and y) that can change, while constants are the numbers that stay the same. Coordinates are pairs of numbers like (3, 4) that tell you exactly where to put a point on your graph.
Quick Tip: Remember coordinates as "across the hall, then up the stairs" - go across the x-axis first, then up or down the y-axis!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
The Two Most Important Parts
Every linear equation has two crucial components that control how your line looks. The slope (m) tells you how steep your line is - it's like the angle of a ramp. If m = 2, your line goes up 2 units for every 1 unit it goes across. Pretty straightforward!
The y-intercept (c) is where your line crosses the vertical y-axis. If c = 3, you know your line will pass through the point (0, 3) every single time. This gives you an instant starting point for drawing your graph.
Understanding these two parts means you can look at any equation like y = 2x + 1 and immediately know: "This line has a slope of 2 and crosses the y-axis at 1." You're already halfway to drawing the perfect graph!
Remember: Positive slopes go uphill from left to right, negative slopes go downhill. It's that simple!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
Creating Your Table of Values
Here's where the real work begins, but don't worry - it's just following a recipe. Start with your linear function in the form y = mx + c. Let's use y = 2x + 1 as our example.
Your mission is to find at least three points that lie on this line. Pick simple x-values like -1, 0, 1, and 2 to make your calculations easy. Nobody wants to work with horrible fractions when they don't have to!
Now substitute each x-value into your equation. When x = 0: y = 2(0) + 1 = 1. When x = 1: y = 2(1) + 1 = 3. When x = 2: y = 2(2) + 1 = 5. See the pattern? Your y-values are increasing by 2 each time because your slope is 2.
Pro Tip: If your three points don't line up perfectly when you plot them, check your maths - one of your calculations has gone wrong!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
Plotting and Drawing Your Graph
Time to bring your calculations to life! Draw your axes with a ruler , label them clearly, and don't forget those arrows on the ends. Your Cartesian plane should look professional.
Plot each coordinate pair from your table carefully. For (-1, -1), go 1 unit left and 1 unit down from the origin. For (0, 1), stay on the y-axis and go 1 unit up. For (1, 3), go 1 unit right and 3 units up.
Once all your points are marked, use your ruler to draw one straight line through them all. Extend the line beyond your points with arrows to show it continues forever. Label your line with its equation - teachers love to see this attention to detail.
Golden Rule: Three points minimum! Two points make a line, but the third point proves you haven't made any mistakes.
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
Worked Example: Positive Slope
Let's tackle y = x + 3 step by step. This linear function has a slope of 1 (remember, x means 1x) and a y-intercept of 3. So you know it goes up gently and crosses the y-axis at 3.
Choose x = -2, 0, and 2 for easy calculations. When x = -2: y = (-2) + 3 = 1. When x = 0: y = (0) + 3 = 3. When x = 2: y = (2) + 3 = 5. Your coordinates are (-2, 1), (0, 3), and (2, 5).
Plot these points and connect them with a straight line. Notice how the line goes up from left to right? That's because your slope is positive. The line crosses the y-axis exactly where you predicted - at y = 3.
Check Yourself: Does your line pass through (0, 3)? If not, something's gone wrong with your plotting!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
Worked Example: Negative Slope
Now let's try y = -2x + 4, which has a negative slope of -2. This means your line will slope downwards from left to right - quite dramatically because -2 is fairly steep. The y-intercept is 4.
Using x = 0, 1, and 2: When x = 0: y = -2(0) + 4 = 4. When x = 1: y = -2(1) + 4 = 2. When x = 2: y = -2(2) + 4 = 0. Your coordinates are (0, 4), (1, 2), and (2, 0).
Plot these points and draw your line. See how it slopes downward? For every step right, the line drops 2 steps down. This linear function creates a perfect straight line that behaves exactly as the equation predicts.
Pattern Spot: Notice how y decreases by 2 each time x increases by 1? That's your slope of -2 in action!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
Exam Success Tips
Master these essentials and you'll smash any linear functions question. Always remember: y = mx + c where m is slope and c is y-intercept. Positive slopes go uphill, negative slopes go downhill. Simple!
Your foolproof method: create a table, pick 3-4 simple x-values, calculate y-values, plot coordinates, and join with a ruler. Label everything clearly - your axes, your line, and its equation. Teachers notice these details.
The y-intercept gives you a brilliant quick check. For y = 2x + 1, your line must cross the y-axis at 1. If it doesn't, you've made an error somewhere. Use this as your safety net in exams.
Exam Hack: If you're running short on time, just find the y-intercept and one other point. Two points are enough to draw the line, though three is always safer!
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
0
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Mock Exam
Quiz
Flashcards
Essay
Most popular content in Mathematics
Most popular content
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.6/5
App Store
4.7/5
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user