A=x2+xy-y2,B=-x2-2xy+y2,当x=1,y=1时,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)
当x=2,y=1 求{(x2+y2)/(x2-2xy+y2)+(2)/xy÷[(1/x)-(1/y)]}÷(x+y)的值
已知A=x2+xy+y2,B=-3xy-x2,求2A-3B的值.
已知x+y=a,xy=b,求x2+y2的值
已知:A=4x2-4xy+y2,B=x2+xy-5y2,求(3A-2B)-(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x-y+1,X2+Y2=25 求(x+y)2和x2-xy+y2的值
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
若X2+Y2-2X-6Y+10=0 ,求(x2-y2)/xy的值