Question

Descompuneti in factori, aplicand formula a^2 - b^2 = (a+b) (a-b)
(x+3y)^2 - 9(x-y)^2
Va rog.

Answer 1

   (x+3y)² - 9(x-y)² =
= (x+3y)² - 3²(x-y)² = 
= (x+3y)² - [3(x-y)]² = 
= [x+3y - 3(x-y)](x+3y + 3(x-y)) = 
= (x+3y-3x + 3y)(x+3y+ 3x - 3y) = 
= (6y - 2x)(4x)

Sper ca te ajuta!