find the sum of the following arithmetic series and write in summation notation

Question

a. 4, 11, ... to 16 terms
b. 19, 13, ... to 10 terms
thank you so much!

Answer 1

a. a = 4 and d = 7
b, a = 19 and d = -6
https://www.mathsisfun.com/algebra/sequences-sums-arithmetic.html

Answer 2

#1.

15
∑ 4+7k
k=0