已知x^2+y^2=18,xy=7,求x+y
已知x=3y,试求(x-y)^2+2xy-y^2/x^2+7xy+y^2
已知X+y=6,xy=7 求x^2y+xy^2=
已知x*x-4xy+4y*y=0 求[2x(x+y)-y(x+y)]/(4x*x-4xy+y*y)的值?
已知xy^2=-2求xy(2x^3y^7+5x^2y
已知x^2+y^2=18,xy=7,求x+y
已知x-xy=8,xy-y=-9,求x+y-2xy的值
已知X/Y=2/7,求x^2-3XY+2Y^2/X^2-2XY+Y^2
已知x/y=7/2,求2x+3xy+2y/x+2xy+y的值
已知1/x-1/y=2,求3x+7xy-3y/2x-3xy-2y
已知1/x-1/y=5 求分式-x+xy+y/2x+7xy-2y
已知1/x-1/y=5,求分式y+xy-x/2x+7xy-2y的值.
已知1/X-1/y=5,求分式(y+xy-x)/(2x+7xy-2y)的值