Question
The value of $\sqrt{-25}\times\sqrt{-9}$ is ___________.

Answer

The value of $\sqrt{-25}\times\sqrt{-9}$ is -15.
Solution:
$\sqrt{-25}\times\sqrt{-9}=\text{i}\sqrt{25}\times\text{i}\sqrt{9}$
$=\text{i}^2(5\times3)=-15$

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