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