Nonlinear functions SAT question

The correct answer is either $-6$ or $4$. The x-intercepts of a graph in the xy-plane are the points where $y=0$. Thus, for an x-intercept of the graph of $y=f(x)$, $0=f(x)$. Substituting $0$ for $f(x)$ in the equation $f(x)=(x+6)(x-4)$ yields $0=(x+6)(x-4)$. By the zero product property, $x+6=0$ and $x-4=0$. Subtracting $6$ from both sides of the equation $x+6=0$ yields $x=-6$. Adding $4$ to both sides of the equation $x-4=0$ yields $x=4$. Therefore, the x-coordinates of the x-intercepts of the graph of $y=f(x)$ are $-6$ and $4$. Note that -6 and 4 are examples of ways to enter a correct answer.