Converge or Diverge?

thatguy47

Junior Member
Joined
Aug 11, 2008
Messages
69
Am I doing these two right?
1.
98864917rn2.jpg

I did the root test and got 11 times (lim n>oo) (3/7). I multiplied 11x(3/7) and got 33/7 which is greater than 1 so it would converge.

Do those problems look right?
 
The first one definitely converges and you are correct.

Here is what it converges to:

\(\displaystyle 11\cdot \frac{\frac{3}{7}}{1+\frac{3}{7}}=\frac{-33}{10}\)

As for the second one, yes it converges as well. You are correct.

What does it converge to?.

\(\displaystyle \frac{6(sin^{2}(1))}{8sin^{2}(1)+1}\)
 
Hello, thatguy47!

Your work is correct!


\(\displaystyle 1.\;\;\sum^{\infty}_{n=1}11\left(\text{-}\tfrac{3}{7}\right)^n\)

\(\displaystyle \text{This is a geomtric series: }\;11\bigg[\left(\text{-}\tfrac{3}{7}\right) + \left(\text{-}\tfrac{3}{7}\right)^2 + \left(\text{-}\tfrac{3}{7}\right)^3 + \hdots\bigg]\)
. . \(\displaystyle \text{with first term }a = \text{-}\tfrac{3}{7}\text{ and common ratio }r = \text{-}\tfrac{3}{7}\)

\(\displaystyle \text{Not only does it converge, but we can find its sum: }\:S \:=\:11\left[\frac{\text{-}\frac{3}{7}}{1-(-\frac{3}{7})}\right] \;=\;-\frac{33}{10}\)


Edit: Too fast for me, galactus!
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