Math Problem Statement

Let f be a function with derivatives of all orders and for which f(2) = 0. The nth derivative of f at x = 2 is given by f^{(n)}(2) = n! / (n ⋅ 3^n). What is the third-degree Taylor polynomial for f about x = 2?

Solution

We are tasked with determining the third-degree Taylor polynomial for the function ff about x=2x = 2. The function has derivatives of all orders, and we are provided with the formula for the nn-th derivative of ff at x=2x = 2:

f(n)(2)=n!n3nf^{(n)}(2) = \frac{n!}{n \cdot 3^n}

Steps:

  1. Calculate the derivatives at x=2x = 2:

    • f(2)=0f(2) = 0 (given)
    • f(2)=1!131=13f'(2) = \frac{1!}{1 \cdot 3^1} = \frac{1}{3}
    • f(2)=2!232=2129=19f''(2) = \frac{2!}{2 \cdot 3^2} = \frac{2 \cdot 1}{2 \cdot 9} = \frac{1}{9}
    • f(3)(2)=3!333=6327=227f^{(3)}(2) = \frac{3!}{3 \cdot 3^3} = \frac{6}{3 \cdot 27} = \frac{2}{27}
  2. Construct the third-degree Taylor polynomial: The formula for the third-degree Taylor polynomial T3(x)T_3(x) centered at x=2x = 2 is:

    T3(x)=f(2)+f(2)(x2)+f(2)2!(x2)2+f(3)(2)3!(x2)3T_3(x) = f(2) + f'(2)(x - 2) + \frac{f''(2)}{2!}(x - 2)^2 + \frac{f^{(3)}(2)}{3!}(x - 2)^3

    Substituting the calculated values:

    T3(x)=0+13(x2)+192(x2)2+2276(x2)3T_3(x) = 0 + \frac{1}{3}(x - 2) + \frac{1}{9 \cdot 2}(x - 2)^2 + \frac{2}{27 \cdot 6}(x - 2)^3

    Simplifying the coefficients:

    T3(x)=13(x2)+118(x2)2+181(x2)3T_3(x) = \frac{1}{3}(x - 2) + \frac{1}{18}(x - 2)^2 + \frac{1}{81}(x - 2)^3

  3. Match with the given options: This matches option B.

Thus, the correct answer is B.


Would you like more details or have any questions? Here are five additional related questions:

  1. What is the general formula for a Taylor series expansion?
  2. How do you find the radius of convergence for a Taylor series?
  3. Why is it important that a function has derivatives of all orders for a Taylor series?
  4. What does the remainder term in the Taylor series tell us about the accuracy of the approximation?
  5. How does shifting the center of expansion (e.g., from x=0x = 0 to x=2x = 2) affect the Taylor polynomial?

Tip: Remember that higher-order terms in a Taylor expansion provide better approximations near the center of expansion.

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Math Problem Analysis

Mathematical Concepts

Taylor Series
Derivatives
Polynomials

Formulas

Taylor Polynomial: T_n(x) = f(a) + f'(a)(x - a) + (f''(a)/2!)(x - a)^2 + ... + (f^{(n)}(a)/n!)(x - a)^n
Given nth derivative: f^{(n)}(2) = n! / (n ⋅ 3^n)

Theorems

Taylor's Theorem

Suitable Grade Level

College level