Question

What is the sum of a 30-term arithmetic sequence where the first term is 73 and the last term is -10? can someone show me how to do this please?

Answer 1

-101 not -10

Answer 2

what is the sum of the first and last term?

Answer 3

-28

Answer 4

what is half of that?

Answer 5

-14

Answer 6

and 30 times -14 is?

the formula that relates to this is just:
\[\frac{n~(first+last)}{2}\]

Answer 7

-420

Answer 8

then -420 it is

Answer 9

Thankyou for your help. That clears things up

Answer 10

good luck