y = (x-1)^2 (x-3) y' = 2(x-1)(x-3) + (x-1)^2 = (x-1)(3x-7)驻点 x = 1， 7/3y'' = 3x-7 + 3(x-1) = 6x-10 , y''(1) < 0 是极大值点。极大值 y(1) = 0
