x2n=5(-2x3n)2 – 3×（-4xn）3=4x3n×2 – 3×（-4xn×3）=4x2n×3 – 3×（-43x2n×3/2）=4(x2n)3  +3×43(x2n) 3/2将x2n=5代入上式：4×53  +3×43×53/2=4×125+3×64×5×51/2=600+960×51/2...