已知x-y=2,xy=-1,求x^2y^4-4x^3y^3+x^4y^2的值

已知x*x-4xy+4y*y=0 求[2x(x+y)-y(x+y)]/(4x*x-4xy+y*y)的值? 已知：x-y=1,xy=-2.求：(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 .已知:x-y=1,xy=-2.求:(-2xy+2 x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 已知1/x-1/y=3,求(3x+4xy-3y)/(x-2xy-y)的值 已知1/x+1/y=3,求3x-4xy+3y/(x+2xy+y)的值 已知x-y=4xy,求x-2xy-y分之2x+3xy-2y的值! 已知3x^2+xy-2y^2=0,求{(x+y)/(x-y)+4xy/(y^2-x^2)}/{(x+3y)*(x-y)} 已知x^2+3xy-4y^2=0(y≠0),求x-y/x+y的值. 已知x+y=5,xy=2,求5x+4y-3y-2y+xy的值 已知x+y=5,xy=2,求5x+4y-3x-2y+xy的值 已知x=y+1,求x^4-xy^3-x^3y+3x^2y-3xy^2+y^4的值 已知x-y=1 求代数式x^4-xy^3-x^3y-3x^2y+3xy^2+y^4的值