Hi Beth. Here is how to approach the problem:
√-2 = √-1 * √2 = i * √2 = √2i
√-18 = √-1 * √18 = √-1 * √9 * √2 = 3√2i
Thus the sum would be √2i + 3√2i = 4√2i
Please note that I am making an important assumption. Can you tell me what that is?
If you have any questions please feel free to post a response.