cases for the formula but I don't understand how to solve for 8x^2 and I think that's where I messed up in my work. I thought that after integrating, I was supposed to plug in 3 and -1 but maybe that was wrong. Can anyone provide some tips/pointers on how to solve this please? Thanks. 1. [0/1 Points] DETAILS PREVIOUS ANSWERS SCALCET9 6.5.001.MI. Find the average value fave of the function f on the given interval. f(x) = 3x + 8x, [-1, 3]