Given the quadratic function f(x)=9x^2-36x+36 find a value of x such that f(x)=9
9x^2-36x+36 = 9
9x^2-36x+27 = 0
Factor. Get two factors from each of the end terms that will add to the value of the middle term.
(3x-9)(3x-3) = 0
Set each factor = 0 and solve.