Video: Zeros of Quadratic Functions

Video Transcript

Given that 𝑓 of 𝑥 is a quadratic function and 𝑥 equals four is a root of the equation 𝑓 of 𝑥 equals zero, what is the value of 𝑓 of four?

We’re told that 𝑥 equals four is a root of the equation. Roots of a function are the 𝑥 intercepts. And the 𝑦-coordinate of points lying on the 𝑥-axis is zero. So the place of the roots are where 𝑓 of 𝑥 equals zero.

The function of 𝑥 equal to zero, 𝑓 of four in this case, is equal to zero. Because 𝑥 equals four is a root of this equation, if we plug in four for 𝑥, the outcome is going to be zero. The function of four equals zero.