Sequences and infinite series
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Sequences and infinite series
A sequence approaches a value term by term.
Repeated approximations can settle toward a target. The index labels discrete observations rather than continuous time.
Explore the idea ↗Interactive lessonPartial sums determine a series' value.
A repeating fractional contribution can add to a finite total. Follow the partial sums instead of only the individual contributions.
Explore the idea ↗Interactive lessonAn infinite sum can be compared with an infinite area.
A decreasing positive sequence of contributions can be bracketed by areas. The same construction also bounds the remainder.
Explore the idea ↗Interactive lessonA known convergent sum can control a smaller one.
A complicated positive term may be bounded by a simpler power-law term. Use that inequality to decide convergence.
Explore the idea ↗Interactive lessonA factorial can outrun an exponential.
Terms involving factorials can initially grow, yet eventually shrink rapidly. Inspect how one term compares with the next.
Explore the idea ↗Interactive lessonA root test exposes an exponential factor.
An nth root can separate exponential growth from slower polynomial effects. Its limiting value decides most cases.
Explore the idea ↗Interactive lessonCancellation can produce conditional convergence.
Positive and negative contributions can settle even when the sum of their magnitudes grows without bound.
Explore the idea ↗Interactive lessonAn infinite polynomial has a convergence interval.
A finite polynomial can be evaluated anywhere, but an infinite series may represent a function only inside a specific radius.
Explore the idea ↗Interactive lessonMatch more derivatives to improve a local approximation.
An exponential response can be approximated near zero by a line, a quadratic, or a higher-degree polynomial. Compare error as you change degree.
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