Complex Simultaneous Systems and Function Analysis
Non-linear simultaneous equations like y+4x+1=0 and y2+5x2+2x=0 require substitution techniques. Replace the linear equation into the quadratic to create a solvable form, then work backwards to find both variables.
Disguised quadratics appear in equations like $2x^4 - 15x^2 - 50 = 0.Bysubstitutinga = x^2,thisbecomes2a^2 - 15a - 50 = 0,whichfactorsas2a+5a−10 = 0$. Remember to convert back to find the original variable.
Sketching quadratic functions requires identifying key features: vertex coordinates, y-intercept, and line of symmetry. For f(x)=11−4x−2x2, completing the square gives $13 - 2x+1^2,showingvertex(-1, 13)andlineofsymmetryx = -1$.
Proving positivity uses completed square form. Since (x−3)2≥0 for all real x, expressions like x2−6x+10=(x−3)2+1 are always positive because they equal (x−3)2+1≥1>0.
Key Tip: For surd form answers, always rationalise denominators and simplify completely - examiners expect exact forms, not decimals.