Bradford T. answered 11/27/20
Retired Engineer / Upper level math instructor
For the mean value theorem to be satisfied, it must be continuous on [-1,1].
It is discontinuous at x = 0.
lim x→0- 1/x = -∞
lim x→0+ 1/x = +∞
also f '(c) = -1/c2 = (1-(-1))/(1-(-1)) = 1 --> c = √-1 which is not ∈R