¿por qué no

listen to the pronunciation of ¿por qué no
Испанский Язык - Английский Язык
why not

A nice day, isn't it? Why not go out for a walk? - Hace un buen día, ¿no crees? ¿Por qué no salimos a dar un paseo?

Why not apologize and ask for his pardon? - ¿Por qué no te disculpas y pides perdón?

Used to state that one has no objection to and approves of a proposal

Let's have pizza for lunch. — Yes, why not?.

Why is that not true?

I don't want to go out today. — Why not?.

Used to introduce a proposal

Why not try turning the handle in the other direction to see if that opens the window?.