Direct Comparison Test: If 0 le a_n le b_n and ∑bn converges, what can you conclude?
∑an converges.
Direct Comparison Test: If 0 le a_n le b_n and ∑an diverges, what can you conclude?
∑bn diverges.
Limit Comparison Test: What is the limit to evaluate?
limn→∞bnan
Limit Comparison Test: What conclusion can be drawn if limn→∞bnan=c, where 0 < c < \infty?
Both ∑an and ∑bn either converge or diverge.
What is the formula for the nth term of a geometric series?
arn−1
When does a p-series converge?
When p>1
When does a p-series diverge?
When p≤1
When does a geometric series converge?
When ∣r∣<1
What are the differences between the Direct Comparison Test and the Limit Comparison Test?
Direct Comparison: Requires direct inequality (an≤bn). Limit Comparison: Compares the limit of the ratio of terms. Direct Comparison: More straightforward when applicable. Limit Comparison: Useful when direct inequality is hard to establish.
Compare and contrast p-series and geometric series.
p-series: Form ∑np1, converges if p>1. Geometric series: Form ∑arn, converges if ∣r∣<1. Both: Useful for comparison tests. p-series: Depends on exponent p. Geometric series: Depends on common ratio r.
Compare Direct Comparison Test when an<bn and ∑bn converges vs. when ∑an diverges.
∑bn converges: Implies ∑an converges. ∑an diverges: Implies ∑bn diverges. The first shows convergence, the second shows divergence.
Compare Limit Comparison Test when the limit is a finite positive number vs. when the limit is zero or infinity.
Finite positive number: Both series behave alike (both converge or both diverge). Zero or infinity: The test is inconclusive and a different comparison series must be found.
Compare using bn=np1 with p>1 and p≤1 in comparison tests.
p>1: ∑bn converges, useful for showing convergence of a smaller series. p≤1: ∑bn diverges, useful for showing divergence of a larger series.
What are the similarities and differences between Direct Comparison Test and Integral Test?
Direct Comparison: Compares series to another series. Integral Test: Relates series convergence to integral convergence. Both: Used to determine convergence/divergence. Integral Test: Requires function to be continuous, positive, and decreasing.
Compare the conditions for convergence of a geometric series with r=0.5 and r=2.
r=0.5: Converges because |0.5| < 1. r=2: Diverges because |2| > 1. Convergence depends on the absolute value of r being less than 1.
Compare using Direct Comparison with an and bn where an is always greater than bn.
If an>bn and ∑an converges, the test is inconclusive. If an>bn and ∑bn diverges, then ∑an diverges.
Compare the usefulness of comparison tests for series with alternating signs vs. series with only positive terms.
Comparison tests are typically used for series with positive terms. Alternating series often require the Alternating Series Test.
Compare the difficulty of applying the Direct Comparison Test when the inequality is obvious vs. when it requires manipulation.
Obvious inequality: Application is straightforward. Requires manipulation: More complex, requires algebraic skills to establish the inequality.
Define Direct Comparison Test.
Compares a series to another known series to determine convergence/divergence. If 0 le a_n le b_n and ∑bn converges, then ∑an converges. If ∑an diverges, then ∑bn diverges.
Define Limit Comparison Test.
Compares the limit of the ratio of two series terms. If limn→∞bnan=c, where 0 < c < \infty, then both series either converge or diverge.
Define Convergence.
A series converges if the sequence of its partial sums approaches a finite limit.
Define Divergence.
A series diverges if the sequence of its partial sums does not approach a finite limit.
Define p-series.
A series of the form ∑n=1∞np1, where p is a real number.
Define Geometric Series.
A series of the form ∑n=0∞arn, where a is a constant and r is the common ratio.
What is a series?
The sum of the terms of a sequence.
Define an and bn in the context of comparison tests.
an and bn are the terms of the two series being compared. They must be non-negative for comparison tests to be valid.
What does it mean for a limit to be 'finite'?
A finite limit is a real number (not infinity).
Define 'end behavior' in the context of series.
How the terms of a series behave as n approaches infinity.