2x-5y=21,y=-x x、y等于多少

2x-5y=21,y=-x x、y等于多少 x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 2x+y=4 x+2y=5 x+y等于?2x+y=4x+2y=5x+y等于? 3x-2y等于75 3y-2x等于5 x=?Y=? 若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 {6(x-y)-7(x+y)=21 {2(x-y)-5(x+y)=-1 x-y/3=x+y/2 2x-5y=7等于多少 已知x+y=6,x-y=5,则x^2-y^2等于多少 已知x+y=2,xy=-5则x分之y+y分之x等于 4x+5y=105,2x+3y=178,x,y等于 如果|x-2y+1|+|2x-y-5|=0 .x+y等于几 |x|=3 |y|=5 |x-y|=|x|+|y| 求 X+Y和 X-Y 等于多少 设x大于1,y大于0,x^y+x^-y=2根号二,x^y-x^-y等于? 已知x、y满足y²=-x²+2x-5/4-y,代数式xy/x+y等于多少 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) y*y*y*y+2x*x*x*x=4x*x*y 求x等于几,y等于几,写出所有选项! 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=?