I don't understand this

Consider the function at) : 4 2:132 on the interval [5, 5]. Find the average or mean slope of the function on this interval, i.e. \"5) ' \"5) -l: 5 (5) _ By the Mean Value Theorem, we know there exists a c in the open interval (5, 5) such that f'(c) is equal to this mean slope. For this problem, there is only one c that works. Find it. E