After I installed Homebrew, 

Then I try the *brew doctor* command, there comes warnings:

[![enter image description here](https://i.stack.imgur.com/oDfZg.jpg)](https://i.stack.imgur.com/oDfZg.jpg)

[![enter image description here](https://i.stack.imgur.com/313xK.png)](https://i.stack.imgur.com/313xK.png)

Could I know the reasons and How to fix it? Could I just ignore these warnings?