30x=4/5y 40(x-1)=y+25 1/3(x+y)=33-1/2x=2(3-1/2y)
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
化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1
{3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1
已知x=1/3,y=-1/2,求代数式x-(x+y)+(x+2y)-(x+3y)+(x+4y)-(x+5y)+...-(
(3x-y)^2+(3x+y)(3x-y),x=1,y=-2
解方程组:(0.2x+0.1y)/2- (4x-y)/10=(x-y)/5+ (3x+0.5y)/30 (3x+2y-1
已知:3x=8y.求(1)x+y/y (2)2x+3y/x-2y
2(x+y) 3x+3y=24 x+y/2x x y/2y= 1
[(2x+y)^2+(y+2x)(y-2x)-2y(4x-y)]/4y,其中x=1/2,y=1/3
3x-2y=1 4x-5y
先化简,再求值:[(x+y)(x-y)-(x-y)^2+2y(x-3y)]/(-4y),其中x=1,y=-2
9y=3x-(x-1),4(x+y)-(2x+4)=8y