Question

Jika x pangkat2 - y pangkat2 = 45
x+y = 9 , tentukan nilai xy...

Answer 1

X^2 + y^2 = 45
(x + y)(x - y) = 45
9.(x - y) = 45
(x - y) = 5

(x + y)^2 = 9^2
x^2 + 2xy + y^2 = 81 ... (1)

(x - y)^2 = 5^2
x^2 - 2xy + y^2 = 25 ... (2)

(1) dan (2) eliminasi
4xy = 56
xy = 56 / 4
xy = 14