不解方程2x+y=5;x-3y=1,求7y(x-3y)²-2(3y-x)³的值.

分类: 作业答案 • 2021-12-20 06:09:24

问题描述：

答

7y(x-3y)²-2(3y-x)³
=7y(x-3y)²+2(x-3y)³
=(x-3y)²[7y+2(x-3y)]
=(x-3y)²[7y+2x-6y)]
=2x+y
=5

答

7y(x-3y)²-2(3y-x)³
=7y(x-3y)²+2(x-3y)³
=（x-3y）²×（7y+2x-6y）
=1×5
=5

答

7y(x-3y)²-2(3y-x)³
=7y(3y-x)²-2(3y-x)³
=(3y-x)²[7y-2(3y-x)]
=(3y-x)²(7y-6y+2x)
=(3y-x)²(y+2x)
=(1)*(5)
=5

答

7y+2