## Elementary Algebra

{$-4,4$}
Simplifying the expression through division and then applying square root on both sides, we obtain: $4x^{2}=64$ $x^{2}=\frac{64}{4}$ $x^{2}=16$ $\sqrt {x^{2}}=\pm\sqrt {16}$ $\sqrt {x^{2}}=\pm\sqrt {4^{2}}$ $x=\pm 4$ Therefore, the solution set is {$-4,4$}.