Which is a zero of the quadratic function f(x) = 16x2 32x − 9?

A zero of a function is the value of x for which f(x) = 0
f(x) = 16x^2 + 32x - 9 = 0
16x^2 - 4x + 36x - 9 = 0
(16x^2 - 4x) + (36x - 9) = 0
4x(4x - 1) + 9(4x - 1) = 0
(4x + 9)(4x - 1) = 0
4x + 9 = 0 and 4x - 1 = 0
4x = -9 and 4x = 1
x = -9/4 and x = 1/4