Question

sabendo que xy=15, calcule (x-y)² - (x+y)²

Answer 1

(x-y)²-(x+y)²= 

x²-2xy+y² -(x²+2xy+y²)

x²-2xy+y²-x²-2xy-y²

-2xy-2xy

-4xy  ( xy= 15)

-4(15)

-60