{6(x-y)-7(x+y)=21 {2(x-y)-5(x+y)=-1
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
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
解方程组(x+y)(x-2y)=-5 (x-y)(x+2y)=7
6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5
若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于
{3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1
已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y)
若2x-3y+4=0则x(x*x-1)+x(5-x*x)-6y+7
化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1
{2x-5y=21,{2x+y=6 {x-3y=1 {y=-2x+3 y=-x; y=1/2x+1 5x-9y=-13
若x、y满足2x+y=6,x-3y=1,求7y(x-3y)²-2(3y-x)³的值
【2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2】/2(x-y)^2=