Math Problem Statement

Evaluate limit when x approaches to 5 and the function is (x^7-5^7)/(x-5)

Solution

To evaluate the limit limx5x757x5\lim_{{x \to 5}} \frac{{x^7 - 5^7}}{{x - 5}}, we can use L'Hôpital's Rule. This rule is applicable when the limit results in an indeterminate form like 00\frac{0}{0} or \frac{\infty}{\infty}.

Given the function:

f(x)=x757x5f(x) = \frac{{x^7 - 5^7}}{{x - 5}}

we first substitute x=5x = 5:

f(5)=575755=00f(5) = \frac{{5^7 - 5^7}}{{5 - 5}} = \frac{0}{0}

This is an indeterminate form, so we apply L'Hôpital's Rule, which states that:

limxcf(x)g(x)=limxcf(x)g(x)\lim_{{x \to c}} \frac{{f(x)}}{{g(x)}} = \lim_{{x \to c}} \frac{{f'(x)}}{{g'(x)}}

if the limit on the right-hand side exists. Here, f(x)=x757f(x) = x^7 - 5^7 and g(x)=x5g(x) = x - 5.

First, we find the derivatives:

f(x)=ddx(x757)=7x6f'(x) = \frac{d}{dx}(x^7 - 5^7) = 7x^6

g(x)=ddx(x5)=1g'(x) = \frac{d}{dx}(x - 5) = 1

Now we apply L'Hôpital's Rule:

limx5x757x5=limx57x61=756\lim_{{x \to 5}} \frac{{x^7 - 5^7}}{{x - 5}} = \lim_{{x \to 5}} \frac{{7x^6}}{1} = 7 \cdot 5^6

Calculating 565^6:

56=156255^6 = 15625

Thus:

715625=1093757 \cdot 15625 = 109375

Therefore, the limit is:

109375\boxed{109375}

Would you like more details or have any questions? Here are some related questions you might be interested in:

  1. How do you evaluate limits using L'Hôpital's Rule?
  2. What are the conditions for using L'Hôpital's Rule?
  3. Can you provide an example of evaluating a limit without L'Hôpital's Rule?
  4. How do you find the derivative of a polynomial function?
  5. What are indeterminate forms in limits?

Tip: Always check the form of a limit before applying L'Hôpital's Rule to ensure it results in an indeterminate form like 00\frac{0}{0} or \frac{\infty}{\infty}.

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Math Problem Analysis

Mathematical Concepts

Limits
L'Hôpital's Rule
Derivatives

Formulas

L'Hôpital's Rule: \(\lim_{x \to c} \frac{f(x)}{g(x)} = \lim_{x \to c} \frac{f'(x)}{g'(x)}\)

Theorems

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Suitable Grade Level

Advanced High School