Mathematics

Problem

Which of the following identities is correct for non-negative real numbers

a

and

b

? a)

\sqrt{a/b}=\dfrac{\sqrt{a}}{b}

\sqrt{a}\,\sqrt{b}=\sqrt{ab}

\sqrt{a+b}=\sqrt{a}+\sqrt{b}

\sqrt{ab}=a\sqrt{b}