利用间接展开法,lgx=lnx/ln10
对lnx展开,先求导,再积分即可
(lnx)′=1/x=1/(1+x-1))=1-(x-1)+(x-1)²-（x-1）³+.
lnx=x-(1/2)(x-1)²+(1/3)(x-1)³+.
lgx=lnx/ln10=1/ln10 {x-(1/2)(x-1)²+(1/3)(x-1)³+.}