Answer
$x \in \{-2, 6\}$
Work Step by Step
$5^{x^2-12}=25^{2x}$
$5^{x^2-12}=5^{4x}$
$x^2-12=4x$
$x^2-4x-12=0$
$x^2+2x-6x-12=0$
$x(x+2)-6(x+2)=0$
$(x-6)(x+2)=0$
$x \in \{-2, 6\}$
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