Answer
($r^{3}$-16)($r^{3}$-5)
Work Step by Step
You are given ($r^{3}$$)^{2}$-21$r^{3}$+80.Factor out:
($r^{3}$$)^{2}$-16$r^{3}$-$5r^{3}$+80 -break out the middle number by finding what numbers add up to -21 and multiply to give 80.The numbers are -16 and -5.
(($r^{3}$$)^{2}$-16$r^{3}$)+($-5r^{3}$+80) -find the GCD of the first two and last two terms-
$r^{3}$($r^{3}$-16)-5($r^{3}$-16) -take ($r^{3}$-16) and factor it out-
The factored expression is ($r^{3}$-16)($r^{3}$-5)
