$$51 a b ( a + 5 ) ( b - 4 ) \div 17 a ( b - 4 )$$
$3b\left(a+5\right)\left(a\left(b-4\right)\right)^{2}$
$15a^{2}b^{3}-24b^{2}a^{3}+48ba^{3}+240ba^{2}+3\left(ab\right)^{3}-120\left(ab\right)^{2}$
