# Geometric series

#### Anemori

is the right equation for S_n= 1+x+x^2+x^3+...+x^(n-1) ?

$$\displaystyle \sum_x^{\infty} \frac{1-x^(n-1)}{1-x}$$

the numerator is 1-x^(n-1)

is the right equation?

thanks!

#### choovuck

you should edit your post cause it's completely confusing.

if you're asking about what is the sum of 1+x+x^2+...+x^(n-1) equal to, then the answer is (1-x^n)/(1-x)

#### Anemori

you should edit your post cause it's completely confusing.

if you're asking about what is the sum of 1+x+x^2+...+x^(n-1) equal to, then the answer is (1-x^n)/(1-x)

I tried to fix it but the exponent of n-1 always messed up.

Thanks for the help, I wasnt sure if i did it right...

Can you give me example using this (1-x^n/1-x) thanks...

#### Prove It

MHF Helper
I tried to fix it but the exponent of n-1 always messed up.

Thanks for the help, I wasnt sure if i did it right...

Can you give me example using this (1-x^n/1-x) thanks...

So you need to write 1 - x^{n - 1} to get $$\displaystyle 1 - x^{n - 1}$$.

#### Anemori

So you need to write 1 - x^{n - 1} to get $$\displaystyle 1 - x^{n - 1}$$.
$$\displaystyle S_n= 1+x+x^2+x^3+...+x^{n-1} ?$$
$$\displaystyle \sum_{x=\infty}^{n-1} a_1 \frac{1-x^n}{1-x}$$
im looking for $$\displaystyle S_7$$ using the the formula. I don't know how to start because I don't have variables for x.