Question

write the series summation notation.
2+5+8+11+ . . .

Answer 1

$$\huge \sum_{k=0}^{n-1} 2+3k $$

as $$ a_n =a+(n-1)d $$
here n goes from 1 to n
so, (n-1) will go from 0 to n-1

replacing n-1 = k

we get, the formual to be 2+3k where k goes from 0 to n-1