Math Problem Statement

The formula lim (h -> 0) [ln(e + h) - 1] / h represents f'(a) for some function f and some number a. Find f(x) and a.

Solution

The problem you shared is about finding a function f(x)f(x) and a value aa based on the given limit:

limh0ln(e+h)1h\lim_{h \to 0} \frac{\ln(e + h) - 1}{h}

This limit looks like the definition of the derivative for some function evaluated at a particular point aa, i.e.,

limh0f(a+h)f(a)h=f(a)\lim_{h \to 0} \frac{f(a + h) - f(a)}{h} = f'(a)

From the expression, we can recognize the form:

limh0ln(e+h)1h\lim_{h \to 0} \frac{\ln(e + h) - 1}{h}

We can see that:

  • The term ln(e+h)\ln(e + h) suggests that the function f(x)=ln(x)f(x) = \ln(x), since its derivative is 1x\frac{1}{x}.
  • The constant 1 in the limit corresponds to ln(e)\ln(e), which is the value of the function at x=ex = e. This means a=ea = e.

Thus:

  • The function f(x)=ln(x)f(x) = \ln(x).
  • The value a=ea = e.

Would you like further details on how this is derived or have any questions? Here are some related questions for practice:

  1. What is the derivative of f(x)=ln(x)f(x) = \ln(x)?
  2. How would you set up the limit definition of the derivative for another function, like f(x)=xf(x) = \sqrt{x}?
  3. What is the importance of recognizing the form of limits as derivative definitions?
  4. How does the natural logarithm function behave around x=ex = e?
  5. Could you apply the same limit process to find the derivative of f(x)=sin(x)f(x) = \sin(x) at some value aa?

Tip: Always try to recognize the structure of limits that represent derivatives—it’s a useful way to solve many calculus problems quickly!

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Math Problem Analysis

Mathematical Concepts

Calculus
Limits
Derivative
Natural Logarithm

Formulas

lim (h -> 0) [f(a + h) - f(a)] / h = f'(a)
Derivative of ln(x) = 1/x

Theorems

Limit Definition of Derivative

Suitable Grade Level

College-level Calculus