Question

Find the sum of the first 9 terms in the arithmetic sequence 45, 40, 35, 30, …

Answer 1

what is the first term and common difference here?

Answer 2

45 -5

Answer 3

ya good:)

Answer 4

:)

Answer 5

...

Answer 6

the formula to find the nth term is
a_n=a_1+(n-1)d
sousing this can you find the 9th term

Answer 7

otherwise directly use this formula to find the sum.
S_n=(2a_1+(n-1)d)*(n/2)

Answer 8

ok

Answer 9

9=45+(9-1)-5

Answer 10

\(a_9=45+(9-1)*(-5)\)
\(=?\)

Answer 11

48

Answer 12

what is 9-1=?

Answer 13

8

Answer 14

ya:)
8*(-5)=?

Answer 15

-48

Answer 16

nope:(

Answer 17

-40

Answer 18

ya:)
-40+45=?

Answer 19

5

Answer 20

Thank you the answer is 5

Answer 21

ya:) that is ur 9th term. nw u knw the first term and last term of the ap whose sum u need to find

Answer 22

the sum=(n/2)*(a_1+a_9)

Answer 23

did u find the sum?

Answer 24

I dont think I need the sum

Answer 25

oh nvm I do need it

Answer 26

45+40+35+30+25+20+15+10+5

Answer 27

225

Answer 28

the question is to find the sum. to do that u can use the formula.
S_n=(n/2)*(a_1+a_n)
=(9/2)(45+5)
=(9/2)(50)
=9*25
=225
u dnt have to write all the terms nd add them
ya u r right:)