已知x^2+y^2=9,xy=-4,求(1)(x+y)^2;(2)(x-y)^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x/y=2,求2x(x+y)-y(x+y)/4x²-4xy+y² 已知x+y=-1,xy=-2,求代数式-5（x+y)+(x-y)+x(xy+y)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-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x-y=3,xy=1,求（-2x+2x+3y)-(3xy+2y-2x)-(x+4y+xy) 已知4x=9y求(1)x+y/y (2)y-x/2x 已知x,y>0 2x+y+3=xy 求5x+4y最小值 已知x^2+y^2+x^2y^2-4xy+1=0 求(x-y)^2008-(xy)^2008 已知1/x-1/y=4,求2x+xy-2y/x-2xy-y的值 已知1/x-1/y=4,求(2x+xy-2y)/(x-2xy-y)