若3x^2+xy-2y^2=0,求（x+y/x-y+4xy/y^2-x^2)除以(x^2+2xy-3y^2/x^2-9y^2)的值

显示全部楼层 · 2009-3-8 17:21:49

千问 · 2009-3-8 17:21:49

3x^2+xy-2y^2=0(3x-2y)(x+y)=0因为4xy/（y^2-x^2）有意义，所以，x+y≠0所以，3x-2y=0y=3x/2（x+y/x-y+4xy/y^2-x^2)除以(x^2+2xy-3y^2/x^2-9y^2)=[(x+y)^2-4xy]/(x-y)(x+y)除以(x+3y)(x-y)/(x-3y)(x+3y)=(x-y)^2/(x-y)(x+y)除以(x-y)/(x-3y)=(x-y)/(x+y)除以(x-y)/(x-3y)=(x-3y)/(x+y)=(x-3*3x/2)/(x+3x/2)=(-7x/2)/(5x/2)=-7/5...