I have been informed that on March 7th from 6:00am to 6:00pm Central Time Lamar University will be doing some maintenance to replace a faulty UPS component and to do this they will be completely powering down their data center.
Unfortunately, this means that the site will be down during this time. I apologize for any inconvenience this might cause.
Paul
February 18, 2026
Section 10.1 : Sequences
2. List the first 5 terms of the following sequence.
\[\left\{ {\frac{{{{\left( { - 1} \right)}^{n + 1}}}}{{2n + {{\left( { - 3} \right)}^n}}}} \right\}_{n = 2}^\infty \] Show SolutionThere really isn’t all that much to this problem. All we need to do is, starting at \(n = 2\), plug in the first five values of \(n\) into the formula for the sequence terms. Doing that gives,
\[\begin{align*}& n = 2:\hspace{0.5in}\frac{{{{\left( { - 1} \right)}^{2 + 1}}}}{{2\left( 2 \right) + {{\left( { - 3} \right)}^2}}} = \frac{{ - 1}}{{13}} = - \frac{1}{{13}}\\ & n = 3:\hspace{0.5in}\frac{{{{\left( { - 1} \right)}^{3 + 1}}}}{{2\left( 3 \right) + {{\left( { - 3} \right)}^3}}} = \frac{1}{{ - 21}} = - \frac{1}{{21}}\\ & n = 4:\hspace{0.5in}\frac{{{{\left( { - 1} \right)}^{4 + 1}}}}{{2\left( 4 \right) + {{\left( { - 3} \right)}^4}}} = \frac{{ - 1}}{{89}} = - \frac{1}{{89}}\\ & n = 5:\hspace{0.5in}\frac{{{{\left( { - 1} \right)}^{5 + 1}}}}{{2\left( 5 \right) + {{\left( { - 3} \right)}^5}}} = \frac{1}{{ - 233}} = - \frac{1}{{233}}\\ & n = 6:\hspace{0.5in}\frac{{{{\left( { - 1} \right)}^{6 + 1}}}}{{2\left( 6 \right) + {{\left( { - 3} \right)}^6}}} = \frac{{ - 1}}{{741}} = - \frac{1}{{741}}\end{align*}\]So, the first five terms of the sequence are,
\[\require{bbox} \bbox[2pt,border:1px solid black]{{\left\{ { - \frac{1}{{13}},\,\, - \frac{1}{{21}},\,\, - \frac{1}{{89}},\,\, - \frac{1}{{233}},\,\, - \frac{1}{{741}},\,\, \ldots } \right\}}}\]Note that we put the formal answer inside the braces to make sure that we don’t forget that we are dealing with a sequence and we made sure and included the “…” at the end to reminder ourselves that there are more terms to this sequence that just the five that we listed out here.