Question

Which geometric series diverges? Three-fifths three-tenths three-twentieths StartFraction 3 Over 40 EndFraction ellipsis Negative 10 4 minus eight-fifths StartFraction 16 Over 25 EndFraction minus ellipsis Sigma-Summation Underscript n = 1 Overscript infinity EndScripts two-thirds (negative 4) Superscript n minus 1 Sigma-Summation Underscript n = 1 Overscript infinity EndScripts (negative 12) (one-fifth) Superscript n minus 1.

Answer 1

The geometric series which diverges is shown in the option number c as the absolute value of the common ratio of this series 4.

$\sum_{n=1 }^{\infty} \dfrac{2}{3}(-4)^{n-1}$

What is geometric series diverges?

Geometric sequence is the sequence in which the next term is obtained by multiplying the previous term with the same number for the whole series.

It can be given as,

$a+ar+ ar^2+ ar^3+...$

Here,

is the (a) first term of the sequence, and (r) is the common ratio.

To be a series as geometric series diverges, it should follow,

$|r| > 1$

First option given as,

3/5+3/10+3/20+3/40+ ...

Here, the common ratio is,

$r=\dfrac{\dfrac{3}{10}}{\dfrac{3}{5}}\\r=\dfrac{1}{2}$

The common ratio is less than one. Thus option a is not correct.

First option given as,

-10+4-8/4+18/25- ...

Here, the common ratio is,

$r=\dfrac{4}{-10}\\r=\dfrac{-2}{5}$

For the option number two the common ratio is (-2/5) which is less than 1. This option is also not correct.

In the option number c, the value of common ratio is -4. The absolute value of common ratio is,

$|r|=|-4|\\|r|=4$

The absolute value of this common ratio is more than one. Thus, this is the correct option.

The geometric series which diverges is shown in the option number c as the absolute value of the common ratio of this series 4.

$\sum_{n=1 }^{\infty} \dfrac{2}{3}(-4)^{n-1}$

Learn more about the geometric sequence here;

brainly.com/question/1509142