Question

Write the value of $\sqrt{-25}\times \sqrt{-9}$.

Answer 1

$$\begin{gathered} \sqrt{-25}\times \sqrt{-9}=5\sqrt{-1}\times 3\sqrt{-1} \\ =5i\times 3i \\ =15i^2 \\ =-15 \end{gathered}$$

Hence, $\sqrt{-25}\times \sqrt{-9}=-15$.