Question

a1=-2 , a2=10

an=

Answer 1

an=a+(n-1)d where d is common difference

Answer 2

can you find the common difference here?

Answer 3

providing its arithmetic...

hope its not geometric...

or even worst...

Answer 4

^^

Answer 5

find general term for geometric sequence

Answer 6

yep usually in questions like these we are provided with 3 terms, here I assumed it is an arithmetic progression

Answer 7

Yea i thought so too at first glance lol

Answer 8

unless we are given a third term, this could be arithmetic or geometric..

Answer 9

it could be d=12 or r=-5

Answer 10

If it is a Geometric progression then

\[\large \boxed {a_n=ar^{n-1}}\]

Answer 11

where r is the common ratio

Answer 12

The formula of the sum of n terms of an arithmetical progression is:

Sn = (a1+an)*n/2, where:

- a1 is the first term of the progression;

- an is the last term;

- n is the number of terms.

Answer 13

Arithmetic: \(a_n=a_1+(n-1)d\) where d=12 and \(a_1\)=-2

Geometric: \(a_n=a_1r^{n-1}\) where r=-5 and \(a_1\)=-2

Answer 14

@higherlearning can you provide us with the full question?

Answer 15

what if the 3rd term is a3 = -1234

Answer 16

@higherlearning you're gonna have to work with us here if you want help, speak up.

Answer 17

@campbell_st ehhh i doubt it...

Answer 18

but its a possibility :D

Answer 19

why not.... think of a number... it could be the 3rd term... I like.-0.316

Answer 20

you guys are confusing me lol

Answer 21

NO, you are confusing.

Answer 22

lol but how? the question is straight forward

Answer 23

We don't have enough info to determine if it is a geometric sequence or Arithmetic sequence? You only gave us two terms, a1 and a2. you never stated: it is an arithmetic or geometric sequence.

Answer 24

okay i have a different one
a1=-4, a2=20

find an in the geometric sequence. i stated it earlier

Answer 25

my first respond stated it is geometric. you must have missed it

Answer 26

there you go... now this makes sense

find the common ratio r

\[r = \frac{a_{2}}{a_{1}}\]

this is easy

Answer 27

then when you know r

\[a_{n} = a_{1} \times r^{n -1}\]

and you know the 1st term

Answer 28

yes, precisely @campbell_st

Answer 29

-5

Answer 30

now you have
r = -5
a1 = -4

Answer 31

thats all you had to say man, that it was geometric\[a_n=-2~(5^{n-1})\]for the first one, this is \(a_n\)

Answer 32

i did lol

Answer 33

thats final?

Answer 34

for the question you posted, yes

Answer 35

@yummydum Precisely right, just speak up :D

Answer 36

you really like that word.. lol

Answer 37

^lol
Precisely
lol cx

Answer 38

thats a good word and thanks dudes

Answer 39

that the final work... except...

Answer 40

I'd write it with a multiplication sign... avoids confusion.