Answer:
-12
Step-by-step explanation:
Because negative numbers are impossible to simplify, we must use imaginary numbers. i=root -1. So, for example to simplify root -9, separate this into root 9 times root -1 which becomes root 9 times i, simplifying to 3i. Repeat this for root -16 to have 3i times 4i. Multiply and get 12i^2. Then, simplify to 12 times -1 because i^2 is root -1 times root -1 making -1. Finally, the answer is -12.
I apologize for this sloppy explanation as I am currently short on time. If you have any questions feel free to ask in the comments and I will try to answer them later!