Here's the question you clicked on:
helpmeplz311
How to Work out the nth term in the sequences below? http://s1274.beta.photobucket.com/user/hmp311/media/7778AD32-3261-48EB-BA9D-119F07AA70C8-1004-00000419CAFB720A_zpsaf8eeb58.jpg.html?sort=3&o=0 Note: I keep asking this and I get a formula: nth term = dn + (a - d)
@lgbasallote @nincompoop
what exactly are you asking?
I dont undersyand how to create a formula.
The worksheet is at the link above.
i see many sequences
It says you have to work out the terms asked for, create a formula.
Actually,all of them. I uave to turn this in today.
well...the formula for arithmetic sequence is what you say \[\huge a_n = a_1 + (n-1)d\] where: an is the last term a1 is the first term n is the number of terms d is the common difference
Please know I am in eight grade.
for example 1, 9, 17, 25, 33,... find the 50th term an would be a50 because a50 is the last term a1 will be 1 because it's the first term n would be 50 because you're looking for the 50th term so you have 50 terms d would be 8 because it adds 8 each number (1 + 8 = 9; 9 + 8 = 17; etc) so if you substitute.. \[\huge a_{50} = 1 + (50 - 1)8\] \[\huge a_{50} = 1 + 49 (8)\] \[\huge a_{50 } = 1 + 392\] \[\huge a_{50} = 393\] so the 50th term is 393 in my example
if you're old enough to learn sequences then you're old enough to learn this
ill write in othere first amd then type it on here.
number 7 is looking for the 50th term not the 44th
You said a1 was the last term,which in this case is 44
i think you're confused... 8, 17, 26, 35, 44, .... this doesn't mean 44 is the last term "..." means the sequence continues 8, 17, 26, 35, 44, 53, 62, 71 and so on
that means the last term is the 50th term because that's what you're looking for make sense?
well, if we erased the 44, would it be correct?
nope. you used 5 as your n
like i said, the sequence doesn't stop at 44 so there are more than 5 terms
since you're looking for the 50th term, there would be 50 terms make sense?
good. so rewrite your solution
wait it shouldve been 50 right
right. now solve it
thatll give me the 50th term?
do you solve for a in the a50?
no... a50 means \(a _{50}\) that means 50th term
just solve the right side
umm,let me tru again
ooo the a50 doesnt matter when solving
you solved 8 + (50-1)9 right?
did you use a calculator?
yes i was supposed to use order of operations?
i see what you did (8 + 50 - 1)* 9
you have to do (50 -1) then multiply it to 9 then add 8
PEMDAS PARENTHESIS expoent MULTIPLICATION division ADDITION subtraction did you forget this?
no, thats what order of operations is
parenthesis is (50 - 1) multiplication is (50-1)*9 addition is 8 + (50-1)*9
that means you do 50 - 1 first
o. so, i use that formula, substitute,and solve right side?
i hope im not in trouble @amistre64
finally got to the end of it :) howdy!
you mean the end of my endless question?
i havent seen the links yet, but lgbas stuff looks good so far yeah, these things can get rather lengthy, but thats the way we like to see them. lots of interaction and studying instead of rote answers
lol, not that i can see :) as long as your trying to learn that material you are fine
they all look to be arithmetic progressions, so you can apply the same techniques to all of them
i'd like to know though @amistre64 do you know what dn + (a-d) means?
it looks like the formula for arithmetic progression....but it looks weird
its another way to express the sequence but for n starting at 0 i believe
amistre can i fan u
dn looks really weird
dn + (a-d) dn - d + a d(n-1) + a
you can fan whomever you wish
i think if i get anymore fans the site will collapse into an infinitly large black hole tho so be careful if you do :)
have you gone over how to find the terms used: a, d, n ?
good, cause one you know how to get those, the rest is just simple arithmetic
d common difference
how do you find the common difference of the sequence?
right, subtract the first term from the second term problem 10: 7 ,13, 19, ... d = 13-7 = 6 right?
and what does the "a" in the formula refer to?
a refers to a term
yes, but there is "a" special a that we need to use in the formula itself. the FIRST term. In the problem im working thru, that would be: 7 d=6, a=7 and what does "n" mean?
im going to use a different but equal notation for the formula: \[f(n)=a+d(n-1)\] \[f(n)=7+6(n-1)\]
you can replace \(f(n)\) with \(a_n\) if you want, its just a placeholder
the "n" is reserved for the position of the term we want to find. in this case, the 90th term \[f(n)=7+6(n-1)\] \[f(90)=7+6(90-1)\] \[f(90)=7+6(89)\] \[f(90)=7+534\] \[f(90)=541\]