Answer
$(x+2y)(x-6y)$
Work Step by Step
$x^{2}-4xy-12y^{2}$
... Searching for two factors of $ac=-12$ whose sum is $b=-4,$
we find$\qquad 2$ and $-6.$
Rewrite the middle term and factor in pairs:
$=x^{2}+2xy-6xy-12y^{2}=$
$=x(x+2y)-6y(x+2y)$
= $(x+2y)(x-6y)$
