通分得到x(x+1) - (x+2) = (x+1)(x+2)x^2 + x - x - 2 = x^2 +3x + 2-2 = 3x + 2x = -(4/3)
通分即可啊
先通分，把分母有理化即可
两方乘以(x+1)(x+2)得x(x+1) - (x+2) = (x+1)(x+2)x^2 + x - x - 2 = x^2 +3x + 2-2 = 3x + 2x = -(4/3)
