求解x+y=a,xx+yy=b,xxxx+yyyy的值?

已知2x=3y,求xy/xx+yy-yy/xx-yy的值 向量内积问题为什么a(x,y,z)、b(x',y',z')的内积a·b=(xx',yy',zz')=xx'+yy'+zz 设集合A=｛x-y,x+y,xy},b={xx+yy,xx-yy,0},且A=B,求实数x与y的值及集合AB 已知xx+yy+4x-6y+13=0,求（xx-2x）/xx+3yy的值. 已知x/(xx+x+1)=a,求xx/(xxxx+xx+1)的值 (x-y)(x+y)(xx-yy)=? 已知x（x+1)-(xx+y)=3,求(xx+yy)/2-xy的值 x(x+1)-(xx+y)=-3,求(xx+yy)/2-xy的值 已知 xx-2x+yy+6y+10=0 求x+y的值 已知(x+y)(x+y)=25,(x-y)(x-y)=9求xy与xx+yy的值 X-Y=4,xy=12则xx+YY的值 x+xx+xxx=xxxx