將等式變形：原式變?yōu)椋╨g（b/c）+lg(a/b)）^2=4;化簡(jiǎn)得：
（lg(b/c)）^2+(lg(a/b))^2=2*lg(a/b)*lg(b/c)；得：(lg(b/c)-lg(a/b))^2=0
得：lg(b/c)=lg(a/b)
所以b/c=a/b
故：a、b、c為等比數(shù)列怎么變?yōu)椋╨g（b/c）+lg(a/b)）^2=4？將等式變形：lg(c/a)=lg(a/b)+lg(b/c)原式變?yōu)椋╨g（b/c）+lg(a/b)）^2=4*lg(a/c)*lg(b/c）;化簡(jiǎn)得：（lg(b/c)）^2+(lg(a/b))^2=2*lg(a/b)*lg(b/c)；得：(lg(b/c)-lg(a/b))^2=0得：lg(b/c)=lg(a/b)所以b/c=a/b故：a、b、c為等比數(shù)列 追問怎么變?yōu)椋╨g（b/c）+lg(a/b)）^2=4？我還是看不懂啊，第一步怎么來的，還有你說（lg（b/c）+lg(a/b)）^2=4 lg（b/c）+lg(a/b)）^2=4*lg(a/c)*lg(b/c），也就是lg(a/c)*lg(b/c)=1？這怎么會(huì)等于1呢用對(duì)數(shù)運(yùn)算公式：lga+lgb=lg（a*b)