已知x+y=7.x2+y2=25,则x·y=
已知x2+4x+y2-2y+5=0,则x2+y2=______.
已知实数x,y满足x2+xy+y2=3,则x2-xy+y2的最小值
已知实数x,y 满足x2+y2+2x=0则x+y得最小值
已知x-y+1,X2+Y2=25 求(x+y)2和x2-xy+y2的值
已知实数x,y满足x2+y2-2x+4y=0,则x2+y2的最小值是
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2x=3y,求xy/(x2+y2)-y2/(x2-y2)的值
已知:x2+y2=25,x+y=7,求x-y.
已知x2-y2=6,x-y=1,则x+y等于( )
已知x2+y2+4x-6y+13=0
我做对了吗.x2(x-y)+y2(y-x)= x2(x-y)-y2(x-y)=x2-y2=(x+y)(x-y)
已知[(x2+y2)-(x-y)2+2y(x-y)]÷4y=1,求4x/4x2-4y2-1/2x+y的值,