Answer
$(5a+3b)(3a-2b)$
Work Step by Step
$15a^{2}-ab-6b^{2}$
... Searching for two factors of $ac=-90$ whose sum is $b=-1,$
we find$\qquad 9$ and $-10.$
Rewrite the middle term and factor in pairs:
$=15a^{2}+9ab-10ab-6b^{2}=$
$=3a(5a+3b)-2b(5a+3b)$
= $(5a+3b)(3a-2b)$
