Find the sum of the following geometric series: `x^3, x^5, x^7, to\ n` terms

Explanation

Let Sn​ be the sum of n terms of the G.P. `x^3,x^5,x^7,..`


Clearly, the given sequence is a G.P. with first term=`a=x^3` and common ratio=`r=x^2 `


Then,
`S_n=(a(r^n-1))/(r-1)`


`S_n​=x^3{(x^2)^n−1​}/(x^2-1)`
...