化简:3(2x2-y2)-2(3y2-2x2).
(2x2-3xy+4y2)+(x2+2xy-3y2)化简(要有过程)
已知(x2+y2+3)(x2+y2-2)-6=0,求x2+y2的值
(x+3y)2+2(x2-y2)(x2+y2)+(x-3y)2.
先化简再求值:-(x2+y2)+[-3xy-(x2-y2)],其中x=-1,y=2.
已知2x+y=7,x2+y2=5,求(4x+2y)2-3x2-y2+2(1-y2)的值.
已知2x=3y,求xy/(x2+y2)-y2/(x2-y2)的值
如果M=3x2-2xy-4y2,N=4x2+5xy-y2,则8x2-13xy-15y2等于( )
已知3x2+2y2=6x,试求x2+y2的最大值.
已知:(x2+y2+1)2-4=0,则x2+y2=______.
已知x2+xy=3,xy+y2=-2,则2x2-xy-3y2的值为( )
已知x,y为实数,且(x2 +y2)(x2 +y2+2)=3.求x2 +y2的值
已知实数x.y满足(x2+y2)(x2+y2-1)=2,求x2+y2的值