Step-by-step explanation:
[tex]\sqrt{ab}=\sqrt{a}\cdot\sqrt{b}\\\\\sqrt{-15}\cdot\sqrt{-4}=\sqrt{(-15)(-4)}=\sqrt{60}=\sqrt{(4)(15)}=\sqrt4\cdot\sqrt{15}=2\sqrt{15}[/tex]
[tex]\text{If the examples are separate.}\\\\\sqrt{-1}=i\\\sqrt{ab}=\sqrt{a}\cdot\sqrt{b}\\\\\sqrt{-15}=\sqrt{(15)(-1)}=\sqrt{15}\cdot\sqrt{-1}=\sqrt{15}\ i\\\\\sqrt{-4}=\sqrt{(4)(-1)}=\sqrt4\cdot\sqrt{-1}=2i[/tex]
