数学解题过程中,把一个等式或不等式变形,往往是一个关键的步骤.变形中巧用两边“取”,犹如添加了“催化剂”,可使问题峰回路转,柳暗花明.一、两边取对数例1在数列an中,a1=3,an+1=a2n,求数列an的通项公式.解由题意an0,在an+1=a2n两边取以3为底的对数,得log3an+1=log3a2n=2log3 Mathematical problem solving process, the transformation of an equation or inequality, is often a key step. The deformation of the clever use of the two sides “take”, as if adding a “catalyst”, can make the problem peak turn, Liu Hanming. One or two sides to take the logarithm Example 1 In the series an, a1=3, an+1=a2n, find the general term formula of the series an. The solution meaning an0, take the base 3 logarithm on both sides of an+1=a2n, and get log3an+ 1=log3a2n=2log3