Answer
(a) $(x+2y)(x+7y)$
(b) $(a-3b)(a-10b)$
Work Step by Step
Part (a):
$x^{2}+9xy+14y^{2}=$
$x^{2}+2xy+7xy+14y^{2}=$
$x(x+2y)+7y(x+2y)=$
$(x+2y)(x+7y)$
Part (b):
$a^{2}-13ab+30b^{2}=$
$a^{2}-3ab-10ab+30b^{2}=$
$a(a-3b)-10b(a-3b)=$
$(a-3b)(a-10b)$