Question

Sendo A = –3xy – 2y e B = 5x + 8y, calcule: a) A . B b) 2B . A

Answer 1

Para  $a=-3xy-2y$  e  $b=5x+8y$  temos:

a)     $a\times b=$

    $=(-3xy-2y)\times (5x+8y)=$

    $=-3xy\times5x-3xy\times8y-2y\times5x-2y\times8y=$

    $=-15x^2y-24xy^2-10xy-16y^2$

b)     $2b\times a=$

    $=2(5x+8y)\times(-3xy-2y)=$

    $=(10x+16y)\times(-3xy-2y)=$

    $=10x\times(-3xy)+10x\times(-2y)+16y\times(-3xy)+16y\times(-2y)=$

    $=-30x^2y-20xy-48xy^2-32y^2$