因为1/[y(1-y/10)]=10/[y(10-y)]=1/y + 1/(10-y)所以，左边不定积分就是ln|y| - ln|10-y|=ln|y/(10-y)|
1/[y(1-y/10)]=10/[y(10-y)]=[1/(10-y)+1/y] 裂项后再积分
