Question

Find the sum of the given arithmetic series.
24 + 17 + 10 + 3 + ... + (-39)

Answer 1

Answer:

-75

Step-by-step explanation:

-39 = 24 +(n-1)(-7)

-39 = 24 +7-7n

-39 = 31-7n

7n = 31+39

7n=70

n=10

the sum = 10/2 × (24-39)

= 5 × -15

= -75