Math Problem Statement

according to the alternating series error estimate, find the smallest m such that the difference between the series (-1)^n/5n^3/2 and the partial sum, sm= (-1)^n/5n^3/2 is less than 0.01

Solution

To solve this problem using the alternating series error estimate, we first need to recall the formula for the error bound in an alternating series.

For an alternating series of the form:

S=n=1(1)nanS = \sum_{n=1}^{\infty} (-1)^n a_n

where ana_n is a decreasing sequence of positive terms that approach 0, the error after taking the partial sum SmS_m (the sum of the first mm terms) is less than or equal to the first omitted term:

SSmam+1|S - S_m| \leq |a_{m+1}|

We are given the series:

S=n=1(1)n5n3/2S = \sum_{n=1}^{\infty} \frac{(-1)^n}{5n^{3/2}}

In this case, an=15n3/2a_n = \frac{1}{5n^{3/2}}, and we want to find the smallest mm such that the error is less than 0.01, i.e.,

am+1=15(m+1)3/2<0.01|a_{m+1}| = \frac{1}{5(m+1)^{3/2}} < 0.01

Step 1: Set up the inequality

We need:

15(m+1)3/2<0.01\frac{1}{5(m+1)^{3/2}} < 0.01

Step 2: Solve for mm

Multiply both sides by 5 to eliminate the denominator:

1(m+1)3/2<0.05\frac{1}{(m+1)^{3/2}} < 0.05

Now, invert both sides:

(m+1)3/2>10.05=20(m+1)^{3/2} > \frac{1}{0.05} = 20

Take the 2/3 power of both sides to solve for m+1m+1:

m+1>202/3m+1 > 20^{2/3}

Using a calculator:

202/38.38520^{2/3} \approx 8.385

So:

m+1>8.385m+1 > 8.385

Thus:

m>7.385m > 7.385

Therefore, the smallest integer mm is m=8m = 8.

Conclusion:

The smallest mm such that the error between the partial sum and the actual sum is less than 0.01 is m=8m = 8.

Would you like more details on how we arrived at this result? Or do you have any questions about this process?


Related Questions:

  1. How do alternating series behave in terms of convergence?
  2. Can this method be applied to non-alternating series?
  3. How do you calculate the sum of an alternating series directly?
  4. What happens if the series is not decreasing or the terms do not approach zero?
  5. How can we use this error estimate to approximate the actual sum more accurately?

Tip: Always check the conditions for using the alternating series error estimate: the terms must be positive, decreasing, and tend to zero as nn \to \infty.

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Math Problem Analysis

Mathematical Concepts

Alternating Series
Error Estimation
Inequalities
Sequences and Series

Formulas

Alternating Series Error Estimate: |S - Sm| ≤ |a_(m+1)|
General term of the series: a_n = 1 / (5n^(3/2))
Inequality setup: 1 / (5(m+1)^(3/2)) < 0.01

Theorems

Alternating Series Error Estimate

Suitable Grade Level

College-Level Calculus or Advanced High School Calculus