Question

si x^2 + y^2=18 y xy=6 entonces (x-y)^2=?

Answer 1

recordar :

(a+b)²=a²+b²-2ab
(a-b)²= a²+b²-2ab

del problema 

(x-y)²=x²+y²-2xy
(x-y)²=  18 - 2(6)
(x-y)²= 6 


saludos Isabela