For this question, we need to simplify some radicals and combine like terms. One thing for sure that should be noticed is the fact that both of these radicals are going to be imaginary, as they both have negatives inside of them.
Let's simplify the radicals:
√-2 = ← Note the negative
i√2
√-18 = ← Note the negative here as well
i√18 =
i√2·3·3 =
i√2·3² =
3i√2
Now, all we have to do is combine like terms:
i√2 + 3i√2 = 4i√2