Question

"Which Term of 127, 122, 117, 112,... is -68 ?"
Its an Arithmetic Problem. Alg 2.
I know the A sub n formula and the S sub n formula i just don't understand how to apply?

Answer 1

Un= 127-5(n-1)
plug in -68 for n

Answer 2

Ok so the \(A_n\) formula is just the formula that states the value of a specific term in the sequence
so \[A_n=A_1+(n-1)d\]
So where A_1 is our first term in the sequence and d stands for the difference btwn each term in the sequence. n stands for the sequence number

Answer 3

So A_1 in our case is 127 .. do you agree???
Thats our first term in the sequence

Answer 4

okay understood but when i plug in 127 for N it gives me An = - 208

Answer 5

Why u plugging in 127 for n????

Answer 6

i mean -68* my bad

Answer 7

So no n doesnt represent -68 ...
-68 =A_n
We wanna find out what our n is
So basically we know the value of the term but what term number is it with regard to the sequence????
SO is it our 30th term in the sequence?? Or is it our 40th term in our sequence???
We dont know so we have to use the formula A_n to find out what our n equals to

Answer 8

just to mention the (a sub n) could be anything, it could be u of n or t of n. Just a variable

Answer 9

yes thats true ...
Im doing a bad job of explaining here -.-

Answer 10

a sub n is like y

Answer 11

find the equation, and plug -67 into An

Answer 12

The equation I stated in the beginning should be right

Answer 13

okay so basically i just have to plug in each number ( 122, 127, 117, 112) as N until one equals -68 ?

Answer 14

Hey lets start from the beggining of sequences ok

Answer 15

no, plug into An, and solve for n

Answer 16

@Mimi_x3 got this :)

Answer 17

So we have an arithmetic sequence that starts with 127, 122, 117, 112 ....
So our first term is \(A_1=127\)
Our second term of the sequence is \(A_2=122\)
Our third term of the sequence is \( A_3=117\)
Our fourth term is \(A_4=112\)
And our sequence just continues on forever
How does this arithmetic sequence work????
Well basically a certain number is subtracted/added from every term and this is known as the difference
How do we find the difference?
We subtract the second term from the first term
\( \text{ Difference } =A_2-A_1=122-127=-5\)
So every -5 is subtracted from the term to get the next term in the sequence
122-127=-5
117-122=-5
112-117=-5
As you can see The way figure out this sequence is by subtracting 5

K so we have this formula:
\[A_n=A_1+(n-1)d\]
\(A_n \)is the value of the term
n represents the sequence number or like what term in the sequence it is
and d represents the difference

So the question is saying -68 is one of the terms in the sequence but what number term is it????

So using the formula where \( A_n=-68\) and d=-5 find plug in these values and solve for n

Answer 18

tsk tsk

Answer 19

Dan lmao

Answer 20

just fukin medal me

Answer 21

@Kainui Pls medal me as Dan refuses to

Answer 22

okay listen to me buddy i want to show u something cool

Answer 23

lmao this buddy doesnt even get the whole sequence thing ..... Ik what u wanna do
SHow how to derive the A_n formula lol

Answer 24

well haha thanks!