Please help me, find the answer

Question

f(x) = 7x³,    [1, 2]

find all values of c in the open interval (a, b) such that f '(c) = f(b)-f(a)/ b-a

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Answer 1

1)

[f(2) - f(1)] / (2 - 1) = ?

2)

f'(c) = ?

Set 1) equal to 2) and solve for c.