I'm guessing the series is supposed to be

By the ratio test, the series converges if the following limit is less than 1.

The first

terms in the numerator's denominator cancel with the denominator's denominator:


also cancels out and the remaining factor of

can be pulled out of the limit (as it doesn't depend on

).

which means the series converges everywhere (independently of

), and so the radius of convergence is infinite.
Answer:
<em>After </em><em>47</em><em> days she will have more than 90 trillion pennies.</em>
Step-by-step explanation:
At the beginning there was 1 penny. At the second day the amount of pennies under the pillow became 2.
The amount of pennies doubled each day. So the series is,

This series is in geometric progression.
As the pennies from each of the previous days are not being stored away until more pennies magically appear so the sum of series will be,

where,
a = initial term = 1,
r = common ratio = 2,
As we have find the number of days that would elapse before she has a total of more than 90 trillion, so









We only need a calculator for this. But, to simplify and make sure you have a good experience here on Brainly, the answer is -0.15. All I did was find 12/80, and added the negative sign. If your issue was that you could not get the negative sign on your calculator, well, there is your answer