x Turn on thread page Beta
 You are Here: Home >< Maths

# Algebraic Sequences watch

1. A linear sequence has common difference of 8. Three consecutive terms in the sequence are added together to give a total of 126. Find the three terms.

So far I've tried this:
8n+8(n+1)+8(n+2)=126
8n+8n+8+8n+16=126
24n+24=126
24n=102
n = 4.25
This is not possible.
I know the answers are 34,42,50 but don't know how to get to them. If they said the expression of the sequence was 8n+x, I may not get this problem. am I wrong?
2. (Original post by bob12344321)
A linear sequence has common difference of 8. Three consecutive terms in the sequence are added together to give a total of 126. Find the three terms.

So far I've tried this:
8n+8(n+1)+8(n+2)=126
8n+8n+8+8n+16=126
24n+24=126
24n=102
n = 4.25
This is not possible.
I know the answers are 34,42,50 but don't know how to get to them. If they said the expression of the sequence was 8n+x, I may not get this problem. am I wrong?
Let's call the 'first' term , then the second term would be and the third would be .

Thence their sum is .

Also, this thread would be better put in the maths forum instead of the maths exam subforum.
3. (Original post by bob12344321)
A linear sequence has common difference of 8. Three consecutive terms in the sequence are added together to give a total of 126. Find the three terms.

So far I've tried this:
8n+8(n+1)+8(n+2)=126
8n+8n+8+8n+16=126
24n+24=126
24n=102
n = 4.25
This is not possible.
I know the answers are 34,42,50 but don't know how to get to them. If they said the expression of the sequence was 8n+x, I may not get this problem. am I wrong?
Your method is wrong, but it's not totally invalid, you just called your first term so
4. (Original post by Zacken)
Also, this thread would be better put in the maths forum instead of the maths exam subforum.
I didn't want to post the thread here but I couldn't find the maths subforum and because I was in a rush I just posted it here, anyways thank you for the answer
5. (Original post by bob12344321)
I didn't want to post the thread here but I couldn't find the maths subforum and because I was in a rush I just posted it here, anyways thank you for the answer
Yeah, that's fine - you're welcome. I was just poinging it out for future reference.

Also, it's the other way around. You've posted in a sub-section of the maths forum.

Your post would be better placed here: http://www.thestudentroom.co.uk/forumdisplay.php?f=38
6. (Original post by bob12344321)
A linear sequence has common difference of 8. Three consecutive terms in the sequence are added together to give a total of 126. Find the three terms.

So far I've tried this:
8n+8(n+1)+8(n+2)=126
8n+8n+8+8n+16=126
24n+24=126
24n=102
n = 4.25
This is not possible.
I know the answers are 34,42,50 but don't know how to get to them. If they said the expression of the sequence was 8n+x, I may not get this problem. am I wrong?
Apologies if you have already sorted it, but I'll give you extra guidence.

First, what does 'common difference' (c.d.) actually mean?

In the sequence 1, 3, 5, 7..., the c.d. is 2 because we are adding 2 each time.
Similiarly, in 5, 9, 13, 17..., the c.d. is 4

In our mystery sequence, we know that the c.d. is 8 (I.e. we add 8 onto the previous term).
Let us call the first term needed n.
Any thoughts on how we might set up our equation?

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: November 15, 2015
Today on TSR

### Negatives of studying at Oxbridge

What are the downsides?

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams