{ x-y/7-x+y/10=1/2 {2(x-y)+5(x+y)=3
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
已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y)
{ x-y/7-x+y/10=1/2 {2(x-y)+5(x+y)=3
化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1
已知x=1/3,y=-1/2,求代数式x-(x+y)+(x+2y)-(x+3y)+(x+4y)-(x+5y)+...-(
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
7x-3y/5=5x-y/3-x+y/2 x-1/5=y+1/3
(4x-2y-z)-{5x[8y-2y-(x+y)]-x+(3y-10z)]=? kuai
10/x+y+3/x-y=-5 15/x+y-2/x-y=-1(用换元法解此方程组)
解方程组(x+y)(x-2y)=-5 (x-y)(x+2y)=7
(3x-y)^2+(3x+y)(3x-y),x=1,y=-2
6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5