∫ a b f ( x ) d x {\displaystyle \int \limits _{a}^{b}f(x)dx}
s n = ∑ i = 1 n a i = a 1 + a 2 + a 3 + . . . + a n {\displaystyle s_{n}=\sum \nolimits _{i=1}^{n}a_{i}=a_{1}+a_{2}+a_{3}+...+a_{n}}
