Question

In terms of n, find the sum of the first n terms of the arithmetic sequence: -4, 5, 14, 23, 32, .....

Answer 1

9n-4

Answer 2

srry, thats not right

Answer 3

Find the difference:
32-23=9, 23-14=9, so d=9


The formula for finding the sum of an arithmetic sequence is
\[S_n=\frac{n}{2}(2a+(n-1)d)\]
where a is the first number (-4) and n is the number you are trying to find.

Answer 4

thats no it either

Answer 5

finaiized has it right

Answer 6

and what would i plug in for d?

Answer 7

The difference which I calculated first.

Answer 8

d=9

Answer 9

oh duh.

Answer 10

and then just solve for n right?

Answer 11

no, leave it in terms of n

Answer 12

oh duh it says that in the questionnnn. I've been up too long. thanks guys!

Answer 13

Yep, Sn is just the total sum, and n is the number you are trying to solve for!