Finding the Zeros of a Quadratic Function
A zero of a function is any number r such that f(r) = 0.
To find the zeros of a function you set your quadratic function equal to zero, factor, and then use the Zero-Product Property to solve. This is exactly what you were doing in the last section; you just may not have known it.
For example, find the zeros of x2 + 3x = 18.
The first step is to set the equation equal to zero.
x2 + 3x – 18 = 0
Factor the quadratic.
(x + 6)(x – 3) = 0
Use the Zero-Product Property.
The zeros of the function are therefore {-6, 3}.x + 6 = 0
x = -6or
x – 3 = 0
x = 3
