Question

X + y + 3(√x+y) = 18
x - y - 2(√x-y) = 15
xy = ?

Answer 1

(√(x + y) + 6)(√(x + y) - 3) = 0
(√(x - y) - 5)(√(x - y) + 3) = 0

ambil yg positif:
√(x + y) = 3
x + y = 9
√(x - y) = 5
x - y = 25

eliminasi:
x + y = 9
x - y = 25
_______ +
2x = 34
x = 17
y = -8
xy = - 136