7x+6y=21 3x+4y=12 问x和y是多少?

7x+6y=21 3x+4y=12 问x和y是多少? 3X+8Y=51 X+6Y=21 问X=?Y=? 21/(x+y)+4/(x-y)=12/(x+y)+7/(x-y)结果为(x+y)/(x-y)=3求过程! 1.（X-Y）/13=Y/7问（x+y）/y=?.2.x/6=y/4=z/3(x.z.y不为0)则（X+3Y）/3Y-2Z=? X/Y=2/5 X+60/Y=4/7 问X.Y各是多少 x－y=4 ｜x｜+｜y｜=7 问x、y的值为多少? (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= {6(x-y)-7(x+y)=21 {2(x-y)-5(x+y)=-1 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 x+y/2+x-y/3=6,4(x+y)-3(x-y)=-20 {(x+y)/2+(x-y)/3=6 4(x+y)-3(x-y)=-20 4(x+y)-3(x-y)=-20,2/x+y+3/x-y=6 （x+y）/2- x-y/2=6 3(x+y)=4(x-y) x+y/3+x-y/2=6 4(x+y)-2(x-y)=40 若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 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= 已知：3x+2y=4+z2x+2z=6+y问是否存在X,Y,Z的正整数值,使X+ Y+Z＜7? 若2x-3y+4=0则x（x*x-1)+x(5-x*x)-6y+7