Question

What is the sum of `sqrt(-81)` and `3sqrt(-25)`?

Answer 1

`-21i, -9i, 9i and 21i` or, in brief, the sum = `(+-6+-15)i`, where i = `sqrt(-1)` .

Explanation:

Separately, the complex numbers are i`sqrt81=+-i9` and i`3sqrt25=3(+-5)i`.
The sum is `=(+-9+-15)i`.