How to prove that the following three tautologies of classical logic are disallowed in intuitionistic logic?

Question

I need to prove that the following three tautologies are disallowed in intuitionistic logic.

The tautologies are:

1-double negation $\neg \neg P\equiv P$

2-Law of excluded middle $P \vee\neg P$

3-Contraposition $(P \supset Q)\equiv (\neg Q \supset \neg P) $

can somebody explain how to do this?