Precalculus (6th Edition) Blitzer

The zeroes of $f$ are $\underline{-1,1}$.
We know that the value of x that makes the output of f zero is known as the zero of a function. Generally, the zero of the function is a coordinate or point of the graph of the function that crosses the $x-$ axis. Therefore, the graph crosses the $x-$ axis at the coordinates $x=-1$ and $x=1$. Hence, the zeroes of $f$ are $x=\underline{-1}$ and $x=\underline{1}$.