ANSWER:
x = 4 and x = -4
STEP-BY-STEP EXPLANATION:
We have the following function:
[tex]f(x)\: =\: 3x^{2}\: -\: 48[/tex]We solve the values of x for when the function is equal to 0, as follows:
[tex]\begin{gathered} \: 3x^{2}\: -\: 48=0 \\ \: 3x^{2}\: -=48 \\ x^2=\frac{48}{3} \\ x=\sqrt[]{16} \\ x=\pm4 \end{gathered}[/tex]