Kapag arithmetic sequence:
[tex]a_n=a_1+(n-1)d \\ S_n= \frac{n(a_1+a_n)}{2} \\ n= \frac{a_n-a_1}{d} +1[/tex]
Dito ang a subn ibig sabihin yun yung nth term, d yung common difference.
Kapag geometric sequence naman:
[tex]a_n=a_1*r^{n-1}[/tex]
[tex]S_n= \frac{a_1(1-r^n)}{1-r} \\ S_{\infty}= \frac{a}{1-r} [/tex]
r yung common ratio
