Question

cuanto es 9xc + 12bc + 15xy + 20by

Answer 1

$9xc + 12bc = 21xb {c}^{2}$

$15xy + 20by = 35xb { y}^{2}$

$21xb { c}^{2} + 35xb {y}^{2} = 56 { x}^{2} { b}^{2} {y}^{2}$

el resultado es:

$56 {x}^{2} {b}^{2} {y}^{2}$