Calculate the derivative at a point using the definition of limit

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2) $f(x) = 4x^3 + 5x^2 - 10x + 4$

$\lim_{x \to 2} \frac{f(x) - f(2)}{x - 2} = f'(2)$

$12x^2 + 10x - 10 + 0 = f'(x)$

$48 + 20 - 10 = 58$

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Step by Step Written Solution

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Step 1

Hi Bildanur, let's solve this calculus problem together. We are asked to evaluate the limit of f of x minus f of two over x minus two, as x approaches two.

Calculating the Limit

$$f(x) = 4x^{3} + 5x^{2} - 10x + 4$$
$$_limit_{x \to 2} \frac{f(x) - f(2)}{x - 2}$$
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Step 2

First, let's recognize that this limit expression is actually the definition of the derivative of the function at the point where x equals two.

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Step 3

So, instead of computing the limit directly, we can find the derivative f prime of x and then substitute two into it.

$$_limit_{x \to 2} \frac{f(x) - f(2)}{x - 2} = f'(2)$$
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Step 4

Let's perform the differentiation. We use the power rule, which says that the derivative of x to the power of n is n times x to the power of n minus one.

Step 1: Find $f'(x)$

$$f(x) = 4x^{3} + 5x^{2} - 10x + 4$$
$$f'(x) = \frac{d}{dx}(4x^{3}) + \frac{d}{dx}(5x^{2}) - \frac{d}{dx}(10x) + \frac{d}{dx}(4)$$
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Step 5

For the first term, four x cubed, the derivative is four times three, which is twelve, times x squared.

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Step 6

Next, the derivative of five x squared is five times two, which is ten, times x.

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About This Question

Subject
Mathematics
Topic
Derivatives
Difficulty
Medium
Question Type
Open Ended

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