Problem: n’th roots

Problem

True or false?

1. \(\sqrt{a+b}=\sqrt{a}+\sqrt{b}\)
2. \(\sqrt{\sqrt[3]{a}}=a^{1/6}\)
3. For \(a>0, a^{1/3}⋅a^3=1\)
4. For \(a>0\) , \(a^{-1/2}=1/\sqrt{a}\)