Hey it looks like you are having some trouble with these problems. I'm not going to do them all for you but I think you should redo the assignment because a lot of these answers are incorrect. When you see a radical (square root) of a negative number always convert it to i's if you can. It is much easier to simplify. So for the first problem it says simplify rad(-16) + rad(-4). So just think of the squareroot of the positive numbers and add an i to the end. So rad(16)i + rad(4)i = 4i + 2i = 6i. Question two is also incorrect. Just do the same thing as the first one. So rad(-16) - rad(-9) = rad(16)i - rad(9)i = 4i - 3i = i. It looks like you were just adding the numbers inside the square root which you cant do. For the i's to the exponents think in groups of 4. So i^1 = 1, i^2 = -1, i^3 = -i and i^4 = 1 and then the cycle repeats. So i^1 = i^5, i^2 = i^6, i^3 = i^7 and i^4 = i^8. So i^7 = -i for problem 9. Hope this helps. Let me know if you have any other questions cause I'm out of time. This stuff can be pretty confusing.