Question

Sendo x² + y² = 12, determine o valor de xy, sendo (x + y)² = 30
A)-9
B)-6
C)6
D)9

Answer 1

Boa dia!

(X+y)^2 = 30

X^2 + 2xy + Y^2 = 30
2xy + 12 = 30
2xy = 18
XY = 9