6(X-Y)-7（x+y)=21

{6(x-y)-7(x+y)=21 {2(x-y)-5(x+y)=-1 6(X-Y)-7（x+y)=21 x+x+y+y+y=21 ,x+x+y+y+y+y+y=27 ,x ,y=? x+x+y+y+y=21 ,x+x+y+y+y+y+y=27 ,x ,y=? 解方程组6(x-y)-7(x+y)=21 2(x-y)-5(x+y)=-1 若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 6（x-y)-7(xy)=21,2(x-y)-5(x+y)=-1 已知x+y=6,xy=7,试求x*x+y*y,x*x-y*y的值 已知：2x+y=6,x-3y=1 求7y(x-3y)(x-3y)-2(3y-x)(3y-x) 4.4x+6y=54 9x+2y=87 5.2x+y=7 2x+5y=19 6.x+24.4x+6y=54 9x+2y=87 5.2x+y=7 2x+5y=19 6.x+2y=21 3x+5y=56 3x+5y-(x+y)=6 2(x+y)-3x=-7 21/(x+y)+4/(x-y)=12/(x+y)+7/(x-y)结果为(x+y)/(x-y)=3求过程! (x-y)的4次方/(y-x)的3次方+(x-y)0的次方*(y-x)+(-x-y)7次方/(x+y)6次方= x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 7x:4y,x:y=( ):( 把(x-y)看作一个整体,化解:5(x-y)+2(x-y)-4(x-y)= 3(x-y)把(x-y)看作一个整体,化解:5(x-y)+2(x-y)-4(x-y)=3(x-y)²-4(x-y)+7(x-y)-6(x-y)²= 、1.2x+9y=81 3x+y=341.2x+9y=81 3x+y=34 2.9x+4y=35 8x+3y=30 3.7x+2y=52 7x+4y=62 4.4x+6y=54 9x+2y=87 5.2x+y=7 2x+5y=19 6.x+2y=21 3x+5y=56 7.5x+7y=52 5x+2y=22 8.5x+5y=65 7x+7y=203 9.8x+4y=56 x+4y=21 10.5x+7y=41 5x+8y=44 11.7x+5y=54 3x+4y=38 12.x+8y=15 化简 x / y(x+y) - y / x(x+y) =