log(a+1)(a+2)=loga(a+2)/loga(a+1).所以要证的就是loga(a+1)＞loga(a+2)/loga(a+1),因为loga(a+1)＞0,所以要证的是[loga(a+1)]²＞loga(a+2).即a^{[loga(a+1)]²}＞a^loga(a+2),即(a+1)^(loga(a+1))＞a+2,...