7/6x-7/6y=20 7/6x+7/6y=170 怎么算

{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 已知x+y=6,xy=7,试求x*x+y*y,x*x-y*y的值 3x+5y-(x+y)=6 2(x+y)-3x=-7 已知：2x+y=6,x-3y=1 求7y(x-3y)(x-3y)-2(3y-x)(3y-x) 若2x-3y+4=0则x（x*x-1)+x(5-x*x)-6y+7 (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= (3x-4y)(5x-4y)-(7x-8y)(6y-5x) 计算：(x-y)^7÷(y-x)^6+(-x-y)^3÷(x+y)^2 3(x+y)的平方-7(x-y)-9(x+y)的平方-6(x-y) 3(x-y)^2-7(x-y)+8(y-x)^2+6(y-x)合并同类项. 2(y-x)的平方-7(x-y)+6(x-y)-3(y-x)的平方 计算(x-y)^7÷(y-x)^6+9-x-y)^3÷(x+y)^2 -6x-y-7x+6x-2y-10x+8y+x+6x-8y的值 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= x-y=13 x=6y-7 X+Y=9 6X+7Y=59 6(X-Y)-7（x+y)=21