Question

If the first term of an arithmetic sequence is 4 and the third term is 18, what is the 23rd term?

Answer 1

Help Please!

Answer 2

Hi! What have you tried so far? (Or are you completely stuck?)

Answer 3

ive trying to do 4+923-1)(18), but its wrong

Answer 4

4+(23-1)(18)

Answer 5

Okay, that's a good start. First of all, if the first term is 4 and the third term is 18, what do you think the second term is?

Answer 6

im not really sure how to figure out the second term that well

Answer 7

Okay, that's no problem! In general, the first term of a series will be A, the second one will be A + D, the third will be A + 2D and so on, so the (n)th term will be A + (n-1)D. You might have used different letters instead of A and D, but I'm guessing you've seen that formula before?

Answer 8

yeah the formula that i was given was an=a1+(n-1)(d)

Answer 9

Great! In that case, in your question, you're told that the first term is 4, so A = 4, and the third term is 18, so A + 2D = 18.
Using that, can you find what D is?

Answer 10

Or would i have to do, an=2(n)-4

Answer 11

Hmm, not sure about that. I'd suggest trying to find D - can you see how?

Answer 12

how do i figure out the second term from the 1st and 3rd

Answer 13

Once you know A and D, you can figure out any term that you like.

Answer 14

(Using your formula).

Answer 15

Just a formula, any formula

Answer 16

The formula you were given was: \[a_{n} = a_{1} + (n-1) d\]

Answer 17

18=4+(3-1)d

Answer 18

yeah basketweave

Answer 19

find out d...u can easily find out the 23rd term.

Answer 20

Okay, so you know that a1 is 4, and a3 is 18, right?

Answer 21

yeah

Answer 22

So using your formula, with n=3, we get\[a_{3}=a_{1}+(3-1)d\]

Answer 23

Can you see how you might find d using that?

Answer 24

(It's ok if you're unsure!)

Answer 25

It's got nothing to do with a2.

Answer 26

that cannot be a2

Answer 27

i need the second term then i will get the difference but i have no clue how to find it

Answer 28

Okay, so a3-a2 = d, and a2-a1=d, right?

Answer 29

If the first term of an arithmetic sequence is 4 and the third term is 18, what is the 23rd term?
A.
92
B.
116
C.
158
D.
161

These are the answers

Answer 30

it should be a3..in ur formula becase u taken n=3... @BasketWeave n u got ur d..add d with first term you got ur 2nd term...

Answer 31

d=7,a=4 find out 23rd term

Answer 32

thanks i can get it form there

Answer 33

I got c

Answer 34

Maybe a picture will help: