Answer
$7(b-5)(b-4)$.
Work Step by Step
The given polynomial is
$=7b^2-63b+140$
Factor out $7$.
$=7(b^2-9b+20)$
Rewrite $-9b$ as $-5b-4b$.
$=7(b^2-5b-4b+20)$
Group the terms.
$=7[(b^2-5b)+(-4b+20)]$
Factor each group.
$=7[b(b-5)-4(b-5)]$
Factor out $(b-5)$.
$=7(b-5)(b-4)$
Hence, the factor of the polynomial is $7(b-5)(b-4)$.
