Math Problem Statement

lim_{h \to 0} \frac{(9 + h)^{-1} - 9^{-1}}{h}

Solution

This is a limit problem that resembles the definition of the derivative of a function at a point. The given expression is:

limh0(9+h)191h\lim_{h \to 0} \frac{(9 + h)^{-1} - 9^{-1}}{h}

This is very similar to the definition of the derivative:

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

Here, we have f(x)=x1f(x) = x^{-1}, and it seems like the point where we are calculating the derivative is x=9x = 9.

Let's solve it step-by-step:

Step 1: Recognize the function

The given expression represents the derivative of the function f(x)=x1f(x) = x^{-1} evaluated at x=9x = 9. The derivative of f(x)=x1f(x) = x^{-1} can be computed as:

f(x)=x2f'(x) = -x^{-2}

Step 2: Compute the derivative at x=9x = 9

The derivative of f(x)=x1f(x) = x^{-1} at x=9x = 9 is:

f(9)=92=181f'(9) = -9^{-2} = -\frac{1}{81}

Step 3: Conclusion

Thus, the value of the limit is:

limh0(9+h)191h=181\lim_{h \to 0} \frac{(9 + h)^{-1} - 9^{-1}}{h} = -\frac{1}{81}

If you'd like further details or have questions, feel free to ask!

Here are 5 related questions:

  1. What is the formal definition of a derivative using limits?
  2. How would this limit change if we had a different function, like f(x)=x2f(x) = x^2?
  3. What happens if we substitute different values for xx in the original function f(x)=x1f(x) = x^{-1}?
  4. Can this limit be solved using L'Hopital's Rule? Why or why not?
  5. How can the power rule of derivatives be applied to functions of the form f(x)=xnf(x) = x^n?

Tip: Remember, recognizing the structure of the problem as the derivative of a function can significantly simplify complex-looking limit problems.

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Math Problem Analysis

Mathematical Concepts

Limits
Derivatives
Calculus

Formulas

f'(x) = lim_{h \to 0} \frac{f(x+h) - f(x)}{h}
f'(x) = -x^{-2}

Theorems

Definition of Derivative

Suitable Grade Level

Grades 11-12 or early college-level calculus