Question

Given a=7,a_13=35, find d and s_13

Answer 1

Step-by-step explanation:

a=7

a+12d=35

7+12d=35

12d=28

d=28/12

d=14/6=7/3.

s13=13/2[14+12(7/3)]

s13=13/2[14+28]

s13=13/2[42]

s13=13*21

s13=273