Question

Given the quadratic function f(x) = x2 – 12x + 36, find a value of x such that f(x) = 9.

Answer 1

They're telling you that f(x) = x^2 - 12x + 36, and they're also tellig you that f(x) = 9

so we can rewrite this to become

x^2 - 12x + 36 = 9

this becomes x^2 - 12x +27 = 0

and then you use your normal solving methods to find x.

Answer 2

so wouldnt the outcome be f(9)=9?

Answer 3

x^2-12x+36=9
x^2-12x+27=0
(x-9)(x-3)=0
x-9=0
x=9

x-3=0
x=3

Therefore, the solution is x=9 and x=3

You prove this by substitution:

x^2-12x+36
(9)^2-12(9)+36
81-108+36=9

(3)^2-12(3)+36
9-36+36=9