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Why do this problem?
The numerical examples should prompt learners to formulate and prove a more general statement and then apply it to these special cases. Going from the particular to the general in problem solving is an important skill for a mathematician.

Inequalities play a big role in advanced mathematics and mathematical research and learners in school will benefit from experience of working with inequalities.

They need to know the Binomial Theorem and the formula for the exponential series and then the problem gives experience of applying these formulae and of proof by mathematical induction.

Possible approach
The first part could be a lesson starter or homework in preparation for a lesson or you could do the first part as a class and set the two numerical examples to be done independently.

Key questions
How do the numerical examples relate to $(1 +\frac{1}{n})^n$?


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Telescoping Series

Find $S_r = 1^r + 2^r + 3^r + ... + n^r$ where r is any fixed positive integer in terms of $S_1, S_2, ... S_{r-1}$.

Climbing Powers

$2\wedge 3\wedge 4$ could be $(2^3)^4$ or $2^{(3^4)}$. Does it make any difference? For both definitions, which is bigger: $r\wedge r\wedge r\wedge r\dots$ where the powers of $r$ go on for ever, or $(r^r)^r$, where $r$ is $\sqrt{2}$?

How Many Solutions?

Find all the solutions to the this equation.

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The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to embed rich mathematical tasks into everyday classroom practice.

NRICH is part of the family of activities in the Millennium Mathematics Project.

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