y=(2-x)/[(1-2x)(1+x)]
=[(1-2x)+(1+x)]/[(1-2x)(1+x)]
=1/(1-2x)+1/(1+x)
1/(1-2x)的n阶导数为
(-1)^n·n!/(1-2x)^(n+1)·(-2)^n
=2^n·n!/(1-2x)^(n+1)
1/(1+x)的n阶导数为
(-1)^n·n!/(1+x)^(n+1)
∴……