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If f(x) = x² - 6x – 10, find f'(-1) using only the limit definition of the derivative.

Options:
A) 3
B) -5
C) 7
D) -7

User Copacel
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1 Answer

7 votes

Final answer:

Using the limit definition of a derivative, f'(-1) for the function f(x) is found to be -11, which does not match any of the given options, suggesting an error in the question or the choices.

Step-by-step explanation:

To find f'(-1) for the function f(x) = x² - 6x – 10 using the limit definition of the derivative, we use the formula:

f'(a) = lim (h → 0) [(f(a+h) - f(a)) / h].

Let's apply this to our function at a = -1:

f'(-1) = lim (h → 0) [((-1+h)² - 6(-1+h) - 10) - ((-1)² - 6(-1) - 10)] / h

= lim (h → 0) [(1 - 2h + h² + 6 - 6h - 10) - (1 + 6 - 10)] / h

= lim (h → 0) [(-3 + h² - 8h) / h]

= lim (h → 0) [h(-3 + h - 8)] / h

After canceling out the h, we get:

= lim (h → 0) [-3 + h - 8]

As h approaches 0, the limit is -3 - 8 = -11.

Therefore, f'(-1) = -11, which is not listed in the given options, indicating a potential error in the question or the options provided.

User Cwap
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