Chapter 7 - Polynomial Equations and Factoring - 7.4 - Solving Polynomial Equations in Factored Form - Exercises - Page 381: 21

The x-coordinates are $x=8$ and $x=-8$.

The graph crosses the x-axis when $y=0$. $\implies y=(x-8)(x+8)=0$ Using zero-product property, we have $(x-8)=0$ or $x+8=0$. Solving for $x$, we obtain $x=8$ or $x=-8$. The x-coordinates are $x=8$ and $x=-8$.