数列极限计算计算lim（(a+b)/ab + (a^2+b^2)/a^2b^2 + … +(a^n+b^n)/a^nb^

s=原式；=lim[(1/a+1/b)+(1/a^2+1/b^2)+。。。+(1/a^n+1/b^n)]=lim[(1/a+1/a^2+。。。+1/a^n)+(1/b+1/b^2+。。。+1/b^n)]=1/(a-1)+1/(b-1)