Question

What is the sum of the arithmetic sequence 135,123,111,... if there are 34 terms? Answers to choose from.

a)-2,176
b)-2,142
c)-2,108
d)-2,074

Answer 1

what is the common difference?

Answer 2

idk

Answer 3

the common difference of an AP is the difference between each term. d = (n-1)term-(n)term

Answer 4

the difference between two consecutive terms is the common difference. What is it?

Answer 5

imreally not sure i dont understand any of this can you guide me though it

Answer 6

lets say i have an AP of 5 terms 1,5,9,13,17

the common difference: d = 5-1 = 9-5 = 13-9 = 17-13 = 4

Answer 7

so what is the common difference for your AP?

Answer 8

7

Answer 9

how did you get 7?

Answer 10

I subtracted all the numbers i had like you did

Answer 11

i did not subtract all the numbers....
5-1 = 4
9 - 5 = 4
13 - 9 = 4
17 - 13 = 4
as you can see, the common difference is constant since it is an AP and it is 4.

I did not subtract all the numbers. I only subtracted two consecutive numbers

Answer 12

it does not matter which terms you choose as long as those two terms are consecutive

Answer 13

oh

Answer 14

i got 7 again

Answer 15

I got a final answer of -2,176 is this correct??

Answer 16

no it is not.
I seriously wonder if you are even trying at all...
I practically gave you the way to find the common difference of the question and you still can give the wrong answer...

Answer 17

d = 123 - 135 = -12
or
d = 111 - 123 = -12

how in the world do you keep getting 7?

Answer 18

i plugged in every thing you have said and my calculator keeps giving me the answers im giving you :(

Answer 19

@hartnn

Answer 20

could you please tell me if i have the correct answer? -2,176

Answer 21

i think that incorrect, what did u get d as ?

Answer 22

originally 7 but irkiz helped me and gave me -12

Answer 23

yes, d=-12
S=34/2 (2*135+33*(-12)) = ?

Answer 24

Okay thank you

Answer 25

oh -2,142 thankyou

Answer 26

yes.
welcome ^_^