{x+y=7 {2x-5y=-21
解方程组(x+y)(x-2y)=-5 (x-y)(x+2y)=7
已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y)
先化简再求值(x-y)(x+y)-(x-2y) 的完全平方+x(3x-5y)-(x-y)(x-2y),其中x=1/2 y
6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5
3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27
若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于
5x+2y=83x-y=7
x-y / 5y= (y-x)^2 / ( )
x+y=3 x+2y=9 3/x+1=y y-x=3 y=2x-3 y-3x=1 2(x+1)-y=6 7x-5y=-9
{2x+y/3-2y=0 2(2x+y)-5=7y
7x-3y/5=5x-y/3-x+y/2 x-1/5=y+1/3
方程2分之x+y+2分之x-y=7,4(x+y)-5(x-y)=2