jika x dan y memenuhi sistem persamaan 2/x+y + 1/2x-y = 2 -4/x+y + 3/2x-y = 1 maka nilai : 2x^2 + xy - y^2 = ....

2/(x + y) + 1/(2x - y) = 2 |2| 4/(x + y) + 2/(2x - y) = 4
.............................................. -4/(x + y) + 3/(2x - y) = 1
--------------------------------------------------------------------- +
........................................................... 5/(2x - y) = 5 => 1/(2x - y) = 1 => 2x - y = 1
2/(x + y) + 1/(2x - y) = 2
2/(x + y) + 1 = 2
2/(x + y) = 1
x + y = 2

Eliminasi
2x - y = 1
x + y = 2
------------- +
3x = 3 => x = 1

x + y = 2 => 1 + y = 2 => y = 1

2x^2 + xy + y^2 = 2(1)^2 + 1(1) + (1)^2 = 2 + 1 + 1 = 4