Question

he axis of symmetry for a quadratic equation can be found using the formula x equals StartFraction negative b Over 2 a EndFraction, where a and b are coefficients in the quadratic equation and x represents the values along a vertical line on the coordinate plane.

What is the equation when solved for a?

Answer 1

Start with x = −b/(2a).

Multiply both sides by 2a: 2ax = −b.

Divide by 2x (x ≠ 0): a = −b/(2x).

Note: if x = 0 then the equation gives 0 = −b/(2a) so b = 0; in that case a can be any nonzero value (a = 0 would not be a quadratic).