∵a/b=10
∴a=10b
∴（lga）²-4lgb=（lg10b）²-4lgb
=（lg10+lgb）²-4lgb
=（1+lgb）²-4lgb
=（lgb）²+2lgb+1-4lgb
=（lgb）²-2lgb+1
关于lg的计算这是怎么推导出来的
∵a/b=10
∴a=10b
∴（lga）²-4lgb=（lg10b）²-4lgb
=（lg10+lgb）²-4lgb
=（1+lgb）²-4lgb
=（lgb）²+2lgb+1-4lgb
=（lgb）²-2lgb+1