Lincoln's mother did what she can him.
实验室用溴和苯反应制取溴苯.得到粗溴苯后,要用如下操作精制:①蒸馏;②水洗;③用干燥剂干燥;④10%NaOH溶液洗.正确的操作顺序是( )
已知a+1a=5,则a2+1a2的值是____ .