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

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

人气：291 ℃　时间：2019-11-19 06:20:05

解答

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