Simplify `sqrt(-16)xxsqrt(-25)`.

Explanation

To simplify the expression \( \sqrt{-16} \times \sqrt{-25} \), we can follow these steps:

### Step 1: Rewrite the square roots
We can express the square roots of negative numbers in terms of \( i \), where \( i = \sqrt{-1} \).
\[ \sqrt{-16} = \sqrt{-1} \times \sqrt{16} = i \times 4 = 4i \]
\[
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