Question

Find a formula for Sn, the sum of the first n terms of the following geometric sequence. Help?

`sqrt3 + 3 + 3sqrt 3+ 9...` using the formula `Sn=u1(1-r^n)/(1-r)`

Answer 1

`S_n=sqrt(3)* (1-(sqrt(3))^n)/(1-sqrt(3))`

Explanation:

`u_1=sqrt(3)`

`r=sqrt(3)`

and you are told:
`color(white)("XXX")S_n=u_1 * (1-r^n)/(1-r)`

so, it's just a matter of substitution.