Practicing Success
The largest term in the sequence $a_n=\frac{n}{n^2+100}$ is: |
$a_5$ $a_7$ or $a_8$ $a_4$ $a_{10}$ |
$a_{10}$ |
$a_n=\frac{1}{n+100/n}$ $a_n$ is maximum if $n+\frac{100}{n}$ is minimum. Now, $E=n+\frac{100}{n}⇒\frac{dE}{dn}=1-\frac{100}{n^2}$ $\frac{dE}{dn}=0⇒\frac{100}{n^2}=1⇒n^2=100⇒n=±10$ Now, $\frac{d^2E}{dn^2}=1+\frac{200}{n^3}⇒(\frac{d^2E}{dn^2})_{n=10}=1+\frac{200}{1000}>0$ ⇒ E has minimum when n = 10 ⇒ $a_n$ is maximum when n = 10 ∴ The largest term of sequence is $a_{10}$. |