记x-5=t,则x=t+5f(x)=1/(t+5) ,展开成t的幂级数即可。=1/[5(1+t/5)]=1/5*[1-t/5+t^2/5^2-t^3/5^3+.....]=1/5-t/5^2+t^2/5^3-t^3/5^4+.....收敛域为|t/5|<1, 即|x-5|<5
