5x-y=3 2x+3y=-9

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 5x=3y,(2x+y)的平方=5x(x+y)+9 3x-2y=9 x-3y=2 x+y=5 x+2y=3 y=x 2x+y=8 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 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 已知X-Y/X+Y=3,求代数式2(x-y)/X+Y-3X+Y/X+Y 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)+...-( 数学题……555{(3x+y)(3x-y)-(x-5y)(5x-y)-(x-2y)²÷(-4x),x=-2.y 解方程组x:y=2:3和5x+3y=38 3y+x/y=8和9y-2x/y=9