{2X-5Y=-3,5X-2Y=-18

已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) x+y/2+x-y/6=5 2(x+y)-3(x-y)=-2 3(x+y)+2(x-y)=36 4(x+y)-5(x-y)=2 4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5 (x-y)/(x+y)=3求( 3x-2y-1)/(x+y-5) 先化简再求值(x-y)(x-2y)+(x-2y)(x-3y)-2(x-3y)(x-4y) x=4 y=5 {(x+y)/2+(x-y)/3=1,(x+y)-5(x-y)=2.求x=?,y=? 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 (计算方程组x+y)/2=6-(x-y)/3,6(x+y)-5(x-y)=18 (4x-2y-z)-{5x[8y-2y-(x+y)]-x+(3y-10z)]=? kuaihuajian 先化简,再求值 [2/3x - 2/x+y（x+y/3x -x-y）]*x/x-y,其中5x+3y=0 先化简,再求值:[3x-2/x+y(x+y/3x-x-y)]/(x-y/x),其中5x+3y=0 x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 3X=5Y （X+Y)*3X=(2Y+X)*4+2*2 5x=3y,(2x+y)的平方=5x(x+y)+9 3x+5y-(x+y)=6 2(x+y)-3x=-7