原式=X^2/(X^4+X^2+1)
=1/(X^2+1+1/x^2)
=1/[(1/X+X)^2-2+1]
=1/(3^2-1)
=1/8
(2)
(2x+3xy-2y)/(x-2xy-y)
分子分母同时除以xy,得：
=[(2/y-2/x)+3]/[(1/y-1/x)-2]
=[-2(1/x-1/y)+3)/[-(1/x-1/y)-2]
=(-6+3)/(-3-2)
=3/5