Answer:
So generally, when you're trying to find the area under the curve, you want to integrate the function within the bounds in question, which in this case is 3 and 5. As a result, you get 4e^x - x^2/2. Then you want to subtract this when you put 3 in for x from when you put 5 in for x, such as the following:
(4e^5-25/2) - (4e^3 - 9/2)
When you combine like terms, you end up with the following answer:
4e^5 - 4e^3 - 8 square units
However, you can approximate the answer to 505.31 square units