Completing the Square: Step by Step
Completing the square transforms any quadratic expression like x2+8x+18 into the neat form (x+a)2+b. This technique makes solving equations and sketching graphs much easier once you've mastered the method.
The process follows three simple steps that work every time. First, divide the x coefficient by 2 to find your 'a' value - so 8÷2 = 4, giving you (x+4)2. Next, subtract a2 from the constant to balance the equation - that's $18-16 = 2.Finally,yougetx+4^2+2$ as your completed square form.
Quick Check: Always expand your completed square back to the original expression to verify you've done it correctly!
When there's a coefficient in front of x2 like $2x^2-8x+15$, you must factorise it out first. Take out the 2 to get $2x2−4x+7.5,thencompletethesquareinsidethebrackets.Thisgivesyou2x−2^2+7$ after simplifying - just remember to distribute that coefficient back through at the end.