Answer
$(x-5+6y)(x-5-6y)$
Work Step by Step
$x^{2}-10x+25-36y^{2}=$
recognize a perfect square in the first three terms
$=(x^{2}-2\cdot 5x+5^{2})-36y^{2}$
$=(x-5)^{2}-36y^{2}$
this is a difference of squares,
$=(x-5)^{2}-(6y)^{2}$
$=(x-5+6y)(x-5-6y)$
