Use the ratio test to determine whether the series converges or diverges.
Table of contents
- 0. Functions7h 52m
- Introduction to Functions16m
- Piecewise Functions10m
- Properties of Functions9m
- Common Functions1h 8m
- Transformations5m
- Combining Functions27m
- Exponent rules32m
- Exponential Functions28m
- Logarithmic Functions24m
- Properties of Logarithms34m
- Exponential & Logarithmic Equations35m
- Introduction to Trigonometric Functions38m
- Graphs of Trigonometric Functions44m
- Trigonometric Identities47m
- Inverse Trigonometric Functions48m
- 1. Limits and Continuity2h 2m
- 2. Intro to Derivatives1h 33m
- 3. Techniques of Differentiation3h 18m
- 4. Applications of Derivatives2h 38m
- 5. Graphical Applications of Derivatives6h 2m
- 6. Derivatives of Inverse, Exponential, & Logarithmic Functions2h 37m
- 7. Antiderivatives & Indefinite Integrals1h 26m
- 8. Definite Integrals4h 44m
- 9. Graphical Applications of Integrals2h 27m
- 10. Physics Applications of Integrals 3h 16m
- 11. Integrals of Inverse, Exponential, & Logarithmic Functions2h 34m
- 12. Techniques of Integration7h 39m
- 13. Intro to Differential Equations2h 55m
- 14. Sequences & Series5h 36m
- 15. Power Series2h 19m
- 16. Parametric Equations & Polar Coordinates7h 58m
1. Limits and Continuity
Introduction to Limits
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Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
For which values of does the series converge?
A
For all real numbers
B
For all such that
C
For all such that
D
For all such that

1
Step 1: Recognize that the problem involves determining the convergence of the infinite series \( \sum_{n=1}^{\infty} \frac{x^n}{n} \). Convergence depends on the behavior of the terms \( \frac{x^n}{n} \) as \( n \to \infty \).
Step 2: Recall the root test or ratio test for series convergence. These tests are often used to analyze series involving powers of \( x \). For this series, the ratio test is particularly useful.
Step 3: Apply the ratio test. The ratio test states that a series \( \sum a_n \) converges absolutely if \( \lim_{n \to \infty} \left| \frac{a_{n+1}}{a_n} \right| < 1 \). Substitute \( a_n = \frac{x^n}{n} \) into the test.
Step 4: Simplify the ratio \( \left| \frac{a_{n+1}}{a_n} \right| = \left| \frac{x^{n+1}/(n+1)}{x^n/n} \right| = \left| x \right| \cdot \frac{n}{n+1} \). As \( n \to \infty \), \( \frac{n}{n+1} \to 1 \), so the ratio becomes \( \left| x \right| \).
Step 5: Conclude that the series converges absolutely if \( \left| x \right| \leq 1 \). However, further analysis shows that the series converges conditionally for \( -1 < x \leq 1 \). This is because the series diverges for \( x = -1 \) due to the alternating harmonic series behavior.
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