Math Problem Statement

For the series S = ∑(5e^(-3n/2)), find the minimum N such that the error of the partial sum S - S_N = R_N ≤ 0.00001.

Solution

The problem is asking to find the minimum value of NN such that the remainder of the series, RN=SSNR_N = S - S_N, is less than or equal to 0.00001, where:

S=n=15e3n2S = \sum_{n=1}^{\infty} 5e^{-\frac{3n}{2}}

This is an infinite series, and we are tasked with estimating how many terms, NN, are needed for the partial sum SNS_N to approximate the total sum SS with an error less than or equal to 0.000010.00001.

Step-by-step approach:

  1. The general term of the series is 5e3n25e^{-\frac{3n}{2}}.
  2. The remainder RNR_N is approximately the next term after the partial sum, i.e., RN5e3(N+1)2R_N \approx 5e^{-\frac{3(N+1)}{2}}, because the series converges exponentially.
  3. We need to solve the inequality 5e3(N+1)20.000015e^{-\frac{3(N+1)}{2}} \leq 0.00001.

Solving for NN:

We need to isolate NN in the inequality:

5e3(N+1)20.000015e^{-\frac{3(N+1)}{2}} \leq 0.00001

Divide both sides by 5:

e3(N+1)20.000015=0.000002e^{-\frac{3(N+1)}{2}} \leq \frac{0.00001}{5} = 0.000002

Now, take the natural logarithm (ln) of both sides:

3(N+1)2ln(0.000002)-\frac{3(N+1)}{2} \leq \ln(0.000002)

Calculate the logarithm:

ln(0.000002)13.8155\ln(0.000002) \approx -13.8155

Thus, the inequality becomes:

3(N+1)213.8155-\frac{3(N+1)}{2} \leq -13.8155

Multiply both sides by -1 (reversing the inequality):

3(N+1)213.8155\frac{3(N+1)}{2} \geq 13.8155

Multiply both sides by 2:

3(N+1)27.6313(N+1) \geq 27.631

Now divide by 3:

N+19.2103N+1 \geq 9.2103

Finally, subtract 1:

N8.2103N \geq 8.2103

Conclusion:

Since we are instructed to round up to the nearest whole number, the minimum value of NN is 9.

Would you like a more detailed explanation or have any further questions? Here are some related topics you might find useful:

  1. What is the concept of convergence in infinite series?
  2. How is the remainder term estimated in a convergent series?
  3. How does exponential decay affect series convergence?
  4. What are some techniques for approximating sums of infinite series?
  5. Can this method be used for other types of series, such as geometric series?

Tip: Always check the remainder term when working with infinite series to ensure accurate approximations.

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Math Problem Analysis

Mathematical Concepts

Infinite Series
Convergence
Exponential Functions

Formulas

S = ∑(5e^(-3n/2))
R_N ≈ 5e^(-3(N+1)/2)

Theorems

Convergence of Infinite Series
Error Approximation in Infinite Series

Suitable Grade Level

College Level or Advanced High School (AP Calculus or beyond)