1.用数学归纳法证明不等式1+1/2+1/3+...1/(2^n-1)>n/2由k推导k+1左边增加的式子是2.等比数列{an}中,首相a1>0,公比q>0,其前n项和为Sn,求证：lgSn+lgSn+2

1、左边增加的式子是 1/2^k+1/(2^k+1)+1/(2^k+2)+.+1/(2^k+2^k-2)+1/(2^k+2^k-1) ,
也就是 1/2^k+1/(2^k+1)+1/(2^k+2)+.+1/[2^(k+1)-1] .
2、因为每项均为正数,因此把待证的不等式转化为 Sn*S(n+2)