I can't seem to figure out a.
For each of the given functions f(x), find the derivative f'(x) at the given point c, first finding a = f'(c). (See Theorem 7, page 156 of the Stewart Essential Calculus textbook)
1. f(x) = 6x + 923; c = -15
f'(c) = 213
2. f(x) = 29 + 27 on the interval [4.5, ∞]; c = 9
f'(c)