Solve: y=4xy = 4xy=4x and x+y=5x + y = 5x+y=5.
(1,4)(1, 4)(1,4)
(4,1)(4, 1)(4,1)
(0,0)(0, 0)(0,0)
(1.25,3.75)(1.25, 3.75)(1.25,3.75)