(2^-2/3) 确定是 2的 -2/3次方?
原式 = [x^2 - 1/4 (3 - 4 y)^2 + 1/12 + 2 y (-3 + 2 y) ]/ (-3 x)^(-1)
= [-(9/4) + x^2 + 6 y - 4 y^2+ 1/12 + 2 y (-3 + 2 y) ] * (-3 x)
=13/2 x - 3 x^3
当x = -1时,原式 = -13/2 + 3 = - 3.5