<PRE><B>Question 697719</B>
a2= 6 and a5= 0.048
&lt;pre&gt;
Use the formula:

a&lt;sub&gt;n&lt;/sub&gt; = a&lt;sub&gt;1&lt;/sub&gt;r&lt;sup&gt;(n-1)&lt;/sup&gt;

First with n=2

a&lt;sub&gt;2&lt;/sub&gt; = a&lt;sub&gt;1&lt;/sub&gt;r&lt;sup&gt;(2-1)&lt;/sup&gt;

6 = a&lt;sub&gt;1&lt;/sub&gt;r&lt;sup&gt;1&lt;/sup&gt;

6 = a&lt;sub&gt;1&lt;/sub&gt;r

{{{6/r}}} = a&lt;sub&gt;1&lt;/sub&gt;

And then with n=5

a&lt;sub&gt;5&lt;/sub&gt; = a&lt;sub&gt;1&lt;/sub&gt;r&lt;sup&gt;(5-1)&lt;/sup&gt;

0.048 = a&lt;sub&gt;1&lt;/sub&gt;r&lt;sup&gt;4&lt;/sup&gt;

{{{0.048/r^4}}} = a&lt;sub&gt;1&lt;/sub&gt;

Equating the expressions for a&lt;sub&gt;1&lt;/sub&gt;

{{{6/r}}} = {{{0.048/r^4}}}

Cross multiplying

6r&lt;sup&gt;4&lt;/sup&gt; = 0.048r

Divide both side by 6r

rł = {{{0.048/6}}}

rł = 0.008

Taking cube roots of both sides

 r = {{{root(3,0.008)}}}

 r = 0.2

Edwin&lt;/pre&gt;


 

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