3y2-x2+(2x-y)-2(x2+3y2),其中x=1,y=-2
已知2x=3y,求xy/(x2+y2)-y2/(x2-y2)的值
先化简再求值:-(x2+y2)+[-3xy-(x2-y2)],其中x=-1,y=2.
解方程组:y2=x3-3x2+2x;x2=y3-3y2+2y
已知:x=3,y=-5,x2-2xy+y2/x2-y2的值是
已知x2+y2+4x-6y+13=0 求x2-2x\x2+3y2
x(x-1)-(x2-y)=-3,求x2-y2-2xy的值
x(x-1)-(x2-y)=-3,求x2+y2-2xy的值
已知x(x-1)-(x2-y)=-3,求x2+y2-2xy的值
已知实数x.y满足(x2+y2)(x2+y2-1)=2,求x2+y2的值
已知2x+y=7,x2+y2=5,求(4x+2y)2-3x2-y2+2(1-y2)的值.
已知圆x2+y2-2x-2y+1=0求x2+y2的最大值
先化简,再求值:2x2+(-x2-2xy+2y2)-3(x2-xy+2y2),其中x=2,y=-12