已知方程组{2x+y=6,x-3y=1,不解方程组,求7y(x-3y)²-(3y-x)²的值.已知方程组{2x+y=6,{x-3y=1.不解方程组,求7y(x-3y)²-(3y-x)²的值.已知方程组{2x+y=6,{x-3y=1.不解方程组,求7y(x-3y)²-(3y-x)³的值。打错了 ..不²是³..
问题描述:
已知方程组{2x+y=6,x-3y=1,不解方程组,求7y(x-3y)²-(3y-x)²的值.
已知方程组{2x+y=6,
{x-3y=1.不解方程组,求7y(x-3y)²-(3y-x)²的值.
已知方程组{2x+y=6,
{x-3y=1.不解方程组,求7y(x-3y)²-(3y-x)³的值。
打错了 ..不²是³..
答
{2x+y=6 ①{x-3y=1 ②①减②得 x+4y=57y(x-3y)²-(3y-x)³=7y(x-3y)²+(x-3y)³=7y(x-3y)²+(x-3y)(x-3y)²=(7y+x-3y)(x-3y)²=(x+4y)(x-3y)²=5x1²=5=5