Question

I get how to find the terms with the equation but not how to find equation with the terms PLease help :) Find an equation for the nth term of the arithmetic sequence.

-20, -16, -12, -8, ...

Answer 1

can ya be more specific?? Do ya want to build /prove the formula
\[T _{n} = a + (n-1)d\] ??

Answer 2

I think so bc these are my choices and I know its not a
an = -20 x 4(n - 1)

an = -20 + 4(n - 1)

an = -20 + 4(n + 2)

an = -20 + 4(n + 1)

Answer 3

so... this is a multiple choice problem...
which means u don;t have to prove that formula...

But do u know about that expression ; i mean the equation to find the nth term ??

Answer 4

all I know is that the first letter is going to be -20 bc that is a1 and the second is adding 4
so the equation will bc an=-20+4 but I don't know what the (n-1) stuff means or to figure out which one I need

Answer 5

Okieee....
this is an arithmetic progression ...
wt is the special feature of an arithmetic progression....
i mean how do u find which one is arithmetic and which one is not if u have 2 progressions ?

Answer 6

im just now starting to teach myself I know its arethmitic when there is a pattern like when youre multiplying the number by 2 to get the next answer I haven't done geometric yet Im just trying to figure out how to find the last bit of that equation and ill most likely learn the other stuff in my next lesson

Answer 7

in an arithmetic progression ya keep adding a constant value to the previous term to find the next term...
if the first term of an arithmetic progression is "x" and the constant value or the difference between 2 successive terms is "y"

1 st term
x + (0xy) = x
2nd term
x + (1 x y) = x + y
3rd term
x + ( 2 x Y ) = x + 2y
4th term
x + (3 x y) = x + 3y

did u get it so far ???

Answer 8

uhm is this how you get this part (n - 1) (n + 2) (n + 1)

Answer 9

yep!!!
did u get it??

Answer 10

I thought the constant value was an = -20 + 4(n + 2) the +4 because that is what we are adding to a1 to get the next term?

Answer 11

yeah!! .... we add that value to get the next value...

Answer 12

but...

Answer 13

what should we do if we have to find 3rd term from the 1st term..

i.e
if the 1st term is 4 and the difference is 2...
we will add 2 to 4 in order to find the 2nd term..
which is 4 + 2 = 6

but to find third term... we will have to add that value again to the 2nd term which is
6 + 2 = 8
but we can write this as...
2nd term + 2 =8
( 4 + 2) + 2 = 8
so what we have done is
4 + (2x2) =8
adding the multiplied difference to the first term...

did u get it ?

Answer 14

so is it this one then ?an = -20 + 4(n + 2)

Answer 15

no.....

Answer 16

dang this last part of the equation is dumb let me try reading over your stuff again

Answer 17

so far...
the example we write can be summarize as follow
nth term = firs term +[ difference x something ]
I think wt troubles u is this "something" part

am I right ?

Answer 18

yea I just don't get how to get the (n-whatever number goes here part)

Answer 19

but I get how to get the rest of the equation up to the part in the parenthesis

Answer 20

so....
lets take the example we right....
if the first term of an arithmetic progression is "x" and the constant value or the difference between 2 successive terms is "y"

1 st term
x + (0xy) = x
2nd term
x + (1 x y) = x + y
3rd term
x + ( 2 x Y ) = x + 2y
4th term
x + (3 x y) = x + 3y

Now observe carefully how we got the 4th term...
remember it should be in the form of ...
nth term = firs term +[ difference x something ]

4th term
x + (3 x y) = x + 3y
x + 3y = x + (3 x y)
here...
nth term is 4 which is x + 3y
so we know what is represent by nth term here

and the first term is x....

and here comes the part u have problem with...
[ difference x something ] = 3y
we know the difference is "Y"
so... the part "something" is equal to = 3
the term (n-1) is the key to find this...
so whatever that part is we should get the answer 3 in this instance...
this term we consider here is 4th term
and the value of that "something" is 3
so..
we can write
"something" = 4th term -1
do u agree with me ?

Answer 21

in the same way if we move to the 3rd term...
x + ( 2 x Y ) = x + 2y
here the [difference x "something"] part is (2 x y)
so.. the something is
2
which means it can be written as
( 3 - 1 )

Answer 22

so ... if u want to find the n th term
the "something" part for n th term can be written as

(n - 1)
so the form can be rearrange as..
nth term = firs term +[ difference x something ]

= first term + [difference x (n-1) ]
did u get it now ???

Answer 23

so its always going to be written like that ? (n-1)?

Answer 24

yeahhhh!!!!

Answer 25

wow awesome thank you ok I have another one same subject different question. if you cant help Its ok jw if you can :)?

Answer 26

u r welcome!!

Answer 27

Find an equation for the nth term of the arithmetic sequence.

a19 = -58, a21 = -164

Answer 28

an = 896 - 53(n - 2)

an = 896 - 53(n - 1)

an = 896 + 53(n + 1)

an = 896 - 53(n + 1)

Answer 29

wait is it b since it has (n-1)?

Answer 30

yep!!!

Answer 31

awesome thank you sir!

Answer 32

no .... wait!! gimme a minute... It could be difference this time

Answer 33

okie

Answer 34

first what is the first term of this progression ...?

Answer 35

ya don't have to calculate it...'cause every answer has the same first term 896

Answer 36

yea I was just gunna say that lol

Answer 37

and obvi youre subtracting 53

Answer 38

so its for sure not c

Answer 39

yeah!! the difference is -53

Answer 40

then we get to the dumb part -_-

Answer 41

and u r correct it is indeed B

Answer 42

ok and for this last problem I have, a word problem is it the same thing just making the equation?
A certain species of tree grows an average of 0.5 cm per week. Write an equation for the sequence that represents the weekly height of this tree in centimeters if the measurements begin when the tree is 800 centimeters tall.

Answer 43

nth term = first term + [ differance x (n-1)]
= 896 -56(n-1)

Answer 44

so its an=800+.05(n-1)?

Answer 45

u got it bro...!!!

Answer 46

sweet thank you so much :)

Answer 47

u r welcome!!