Answer
$(3a-2b)(5a+7b)$
Work Step by Step
$15a^{2}+11ab-14b^{2}$
... Searching for two factors of $ac=-210$ whose sum is $b=21,$
we find$\qquad-10$ and $21.$
Rewrite the middle term and factor in pairs:
$=15a^{2}-10ab+21ab-14b^{2}=$
$=5a(3a-2b)+7b(3a-2b)]$
=$(3a-2b)(5a+7b)$
