3x-7y=-24 x+y=12

3x-7y=-24 x+y=12 21/(x+y)+4/(x-y)=12/(x+y)+7/(x-y)结果为(x+y)/(x-y)=3求过程! 12y(x-y)^2-8(x-y)^3=? 若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 3x+y=2 -y/x+y=123x+y=2 （-y/x）+y=12 解方程组24/(x+y) +24/(x-y) = 7/3 ,8/(x+y) +18/(x-y) = 4/3 2(x-2y)²-7(x-2y)³+3(2y-x)²+(2y-x)³合并同类项 这个式子2（x-2y)²-7（x-2y)³+3(2y-x)²-(2y-x)³=2（x-2y)²-7（x-2y)³+3(x-2y)²+(x-2y)³=5(x-2y)²-6(x-2y)³=(x-2y)²(5-6x+12y) x+y/2+ x-y/2=6 2(x+y)-3x+3y=24 求X Y x-2y=9 x+y+z=7 2x-3y=12 计算3x/(x-3y)+(x+y)/(4y-x)-7y/(x-4y)=? 若x,y为正整数,且满足3x(x+y)-y(x+y)=7,求x,y （x+y-5)*（x+y-5)+（x-y+3)=0 x*x-y*y 已知:3x-5y=0,求x/y,x-y/y,x-y/x 先化简再求值; 解方程组 x(x-y)-y(x+y)+2xy 其中x=2 ,y=-22.x[x-x(x-1)],其中x=-2解方程组4x+3y=12x-y=32.y+1=2x 4x-y=2 3.2x+2y=0 2x-y+24=0 推倒公式:(x+y)(x*x-3x+y*y)=x*x*x+y*y*y怎么做. 已知：2x+y=6,x-3y=1 求7y(x-3y)(x-3y)-2(3y-x)(3y-x) x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 7y(x-3y)-2(3y-x)=0 .x=?,y=?