Which of the following equals for ?

MATHEMATICS · Single correct · AoPS · Mathematics · Follow the Rules · Follow the Rules

Problem

Which of the following equals

\sqrt{a}\,\sqrt{b}

for

a,b\ge 0

? (a)

\sqrt{a}+\sqrt{b}

(b)

ab

(c)

\sqrt{ab}

(d)

\sqrt{a+b}