{x/60+y/80=10,x/60+y/40=15、{2x/3+3y/4=1/5,5x/6-5y/2=2、{5/2(x
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
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)+...-(
(4x-2y-z)-{5x[8y-2y-(x+y)]-x+(3y-10z)]=? kuai
数学题……555{(3x+y)(3x-y)-(x-5y)(5x-y)-(x-2y)²÷(-4x),x=-2.y
若2x-3y+4=0则x(x*x-1)+x(5-x*x)-6y+7
10/x+y+3/x-y=-5 15/x+y-2/x-y=-1(用换元法解此方程组)
已知X,Y,满足(X+3Y)(X-3Y)=-10(Y^2-6/5)和2X(Y-1)+4(1/2X-1)=0
3x+2y/4=2x+y/5=x-y+1/6