X + Y = 2XYX+ Y – (XY)2 = (XY)2 −2XY+2=> 2XY – (XY)2 = (XY)2 −2XY+2 (1)ĐẶT T = (XY)2 −2XY+2 (T ≥ 0)=> 2XY – (XY)2 = 2 – T2
1. x + y = 2xy
x+ y – (xy)
2=
(xy)2
−2xy+2=> 2xy – (xy)
2=
(xy)2
−2xy+2(1)
Đặt t =
(xy)2
−2xy+22
−2xy+22
−2xy+22
−2xy+2