已知x/y=2,求(x+y)2-4xy/x2+y2
已知2x=3y,求xy/(x2+y2)-y2/(x2-y2)的值
已知x2+y2=20,x2+xy-2y2=2(x+2y),求x+y的值
已知x-y+1,X2+Y2=25 求(x+y)2和x2-xy+y2的值
已知x2+4y2+x2y2-6xy+1=0,求 x4-y4/2x-y 乘 2xy-y2/xy-y2 除以(x2+y2/x
已知X2+Y2+8X+6Y+25=0 求代数式X2++XY+4Y2分之X2-4Y2 减X+2Y分之X的值
已知X2-2x+y2+6y+10=0,求(x2-2xy)/(xy+y2)的值
已知x+y=4,xy=2,求x2+y2+3xy的值.
已知x2+y2-2x+4y+5=0,求(x^4-y^4)/(2x^2+xy-y^2)·[(2x-y)/(xy-y^2)]
已知x+y=4,xy=3求(1)x2=y2 (2)x-y的值
已知x2+y2-10x-6y+34=0,求(x-y/x+y)2÷x2-y2/xy×x2+2xy+y2/x2-xy 的值.
已知x+y=8,xy=12,求x2+y2;(x-y)2的值
已知实数x、y满足2x2-7xy+3y2=0,求x:y