若x²y=3,求2xy(x的5次方y的2次方-3x³y-4x)的值

若x²y=3,求2xy(x的5次方y的2次方-3x³y-4x)的值
若x²y=3,求2xy(x的5次方y的2次方-3x³y-4x)的值

若x²y=3,求2xy(x的5次方y的2次方-3x³y-4x)的值
原式=2x^6y³-6x^4y²-8x²y
=2(x²y)³-3(x²y)²-8(x²y)
=2×3³-3×3²-8×3
=3

x的5次方y的2次方=9x
3x³y=9x
2xy(x的5次方y的2次方-3x³y-4x)=-8x²y=-24

2xy(x的5次方y的2次方-3x³y-4x)=2x²y（x的4次方y的2次方-3xxy-4）=2x²y[（x²y-4）（x²y-1）]=-12就是一个配方法