Chapter 7: Problem 8
Evaluate the arithmetic series. $$ \sum_{m=1}^{75}(2+3 m) $$
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Chapter 7: Problem 8
Evaluate the arithmetic series. $$ \sum_{m=1}^{75}(2+3 m) $$
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Explain why $$ \sum_{m=1}^{999}\left(m^{5}-2 m+7\right)=\sum_{k=1}^{999}\left(k^{5}-2 k+7\right) . $$
Show that an infinite sequence \(a_{1}, a_{2}, a_{3}, \ldots\) is an arithmetic sequence if and only if there is a linear function \(f\) such that $$ a_{n}=f(n) $$ for every positive integer \(n\).
Show that $$ \sqrt{n^{2}+n}-n=\frac{1}{\sqrt{1+\frac{1}{n}}+1} $$ [Hint: Multiply the expression \(\sqrt{n^{2}+n}-n\) by \(\left(\sqrt{n^{2}+n}+n\right) /\left(\sqrt{n^{2}+n}+n\right) .\) Then factor \(n\) out of the numerator and denominator of the resulting expression.] [This identity was used in Example 1.]
Show that $$ \frac{1}{2}+\frac{1}{3}+\cdots+\frac{1}{n}<\ln n $$ for every integer \(n \geq 2\). [Hint: Draw the graph of the curve \(y=\frac{1}{x}\) in the \(x y\) plane. Think of \(\ln n\) as the area under part of this curve. Draw appropriate rectangles under the curve.]
Express $$ 8.237545454 \ldots $$ as a fraction; here the digits 54 repeat forever.
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