Answer
$(b+6)(b-12)$
Work Step by Step
$b^2-6b-72$ has no common monomial factors
$=(\ \ \ \ \ \ \ \ )(\ \ \ \ \ \ \ \ )$
$=(b\ \ \ \ \ \ )(b\ \ \ \ \ \ )$
$=(b+\ )(b-\ )$ The factors of -72 must have unlike signs.
$=(b+6)(b-12)$ 6 and -12 have a sum of -6 and a product of -72.
