Question

Sequences and their sum (?) (comments!)

Answer 1

\[\huge {\color{blue} {Formulas.} }\]

Arithmetic: \[\huge {\color{blue} {a_n=a_1+d(n-1)} }\]
Geometric: \[\huge {\color{blue} {t_n=t_1 \times r ^{(n-1)}} }\]

More?

Answer 2

Mmm...lemme see...

Answer 3

Nah, I'm not getting it with these <.>