.Find the G.P., if the common ratio of G.P. is 3, nth term is 486 and sum of first n terms is 728.

Explanation

Let common ratio = r

and let ` a_n`​ be the nth term of G.P

Given that r=3, last term i.e `a_n​=ar^(n−1)=486`

`S_n​=a(r^n−1)/(r-1)`

​=`(rar^(n−1)−a)/(r-1)​=728`

Substituting the values in above equation

=`[(3)xx486−a]/(3-1)​=728`

=`[(3)xx486]​=2 xx728+a`

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