Math Problem Statement

Let f(x) = (2x)^x. Use the limit definition of the derivative to estimate the value of f′(3)

Solution

The limit definition of the derivative states:

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

For the given function:

f(x)=(2x)xf(x) = (2x)^x

we want to estimate f(3)f'(3), so we compute:

f(3)f(3+h)f(3)hf'(3) \approx \frac{f(3+h) - f(3)}{h}

Step 1: Compute f(3)f(3)

f(3)=(2(3))3=63=216f(3) = (2(3))^3 = 6^3 = 216

Step 2: Compute f(3+h)f(3+h) (for a small hh)

f(3+h)=(2(3+h))3+hf(3+h) = (2(3+h))^{3+h}

For estimation, let’s take h=0.001h = 0.001:

f(3+0.001)=(2(3.001))3.001f(3+0.001) = (2(3.001))^{3.001}

Now, we calculate:

f(3)(2(3.001))3.0012160.001f'(3) \approx \frac{(2(3.001))^{3.001} - 216}{0.001}

I will compute this numerically. Define function f(x) = (2x)^x def f(x): return (2 * x) ** x

Define values

x = 3 h = 0.001

Compute derivative approximation using limit definition

f_prime_approx = (f(x + h) - f(x)) / h f_prime_approxUsing the limit definition of the derivative with h=0.001h = 0.001, we estimate:

f(3)603.90f'(3) \approx 603.90

Would you like a more detailed breakdown of the calculations?

Related Questions:

  1. How can we use logarithmic differentiation to find f(x)f'(x) explicitly?
  2. What happens to f(x)f'(x) as xx increases?
  3. Can we approximate f(3)f'(3) more accurately using a smaller hh?
  4. How does the function f(x)=(2x)xf(x) = (2x)^x behave for large xx?
  5. How can we use numerical differentiation techniques to estimate derivatives in general?

Tip:

For functions of the form xxx^x, taking the natural logarithm before differentiating simplifies the process!

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Math Problem Analysis

Mathematical Concepts

Calculus
Derivative
Limit Definition of Derivative
Exponentiation Functions

Formulas

f'(x) = lim(h → 0) (f(x + h) - f(x)) / h

Theorems

Limit definition of derivative

Suitable Grade Level

Grades 11-12