Solve: x−y=0,x+y=4x - y = 0, x + y = 4x−y=0,x+y=4.
(2,2)(2, 2)(2,2)
(1,3)(1, 3)(1,3)
(3,1)(3, 1)(3,1)
(0,0)(0, 0)(0,0)