若A=x2-2xy+1/3y2,B=2x-3xy+y2,其中x=1,y=-2,求2A-B的值
若A=x2-2xy+1/3y2,B=2x-3xy+y2,其中x=1,y=-2,求2A-B的值
已知2x=3y,求xy/(x2+y2)-y2/(x2-y2)的值
A=4x2-2xy+4y2,B=3x2-6xy+3y2,且|x|=3,y2=16,|x+y|=1,求4A+[(2A-B)
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A=x2+xy+y2,B=-3xy-x2,求2A-3B的值.
已知:A=4x2-4xy+y2,B=x2+xy-5y2,求(3A-2B)-(2A+B)的值.
设A=2x2-3xy+y2+x-3y,B=4x2-6xy+2y2+4x-y,若|x-3a|+(y+3)2=0,且B-2A
若X2+Y2-2X-6Y+10=0 ,求(x2-y2)/xy的值
x2-xy-2y2-x-7y-6=(x-2y+A)(x+y+B).求A、B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