x2+2xy-y2=7,则x2+y2的最小值为
若x2+2xy-y2=7则x2+y2的最小值为
已知实数x,y满足x2+xy+y2=3,则x2-xy+y2的最小值
已知x2+xy=3,xy+y2=-2,则2x2-xy-3y2的值为( )
实数xy满足x2+y2+2x-4y+1=0,则x2+y2-2x+1的最小值为
设x、y为实数,且x2+xy+y2=3,求x2-xy+y2的最大值和最小值.
已知x2-xy=7,2xy+y2=4,则代数式x2+xy+y2的值是___.
已知x2+xy=4,xy+y2=12,求代数式x2-y2与x2+2xy+y2的值各为多少
已知2x=3y,求xy/(x2+y2)-y2/(x2-y2)的值
已知x2+y2=7,xy=-2,求5x2—3xy—4y2—11xy—7x2+2y2的值
已知X2+y2=7,Xy=-2,求多项式5X2一3Xy-4y2-11Xy-7X2+2y2的值.
已知:x2+y2=7,xy=-2.求7x2-3xy-2y2-11xy-5x2+4y2的值.
已知x2+xy=-3,xy+y2=7,试求:x2+2xy+y2的值.