2. Let f(x) = x3 – 8, and let g be the inverse function of f. For what value in the domain of g is g not differentiable?
|
A. -8 |
B. -2 |
C. 0 |
|
D. 2 |
E. 8 |
Solution: The answer is A
First find the inverse function of f by the following three steps:
Step 1: Write y = f(x).
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Step 2: Solve for x in terms of y.
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Step 3: Interchange x and y. The resulting equation is the inverse function g in terms of x.
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Differentiate g(x) to find the value in the domain of g where g is not differentiable. In other words, where is g’(x) not defined.

Clearly, g is not differentiable at x = -8.