Question

Se xy = 10 e x² + y² = 29, quanto vale (x + y)² ? E (x - y)² ?

Answer 1

(x+y)²=x²+2x.y+y²
(x+y)²=x²+y²+2xy
(x+y)²=29+2.10
(x+y)²=49

(x-y)²=x²-2xy+y²
(x-y)²=x²+y²-2xy=29-20
(x-y)²=9