Progression

[Wxlauslen123]

To the helpers:
As far as I can tell, "the Tr form" just means the fact given, that T_r = 1+1+2+3+...+(r+4). That is, the rth term is formed by adding r+4 to the previous term, or alternatively, the rth term is 1 + the (r+4)th triangular number. (The notation T_r merely means "the rth term of a sequence called T. It is not some advanced method or concept! The "form" mentioned in the problem is not "T_r", but "1+1+2+3+...+(r+4)".)

To @Wxlauslen123:
I can't tell, without knowing what you have been learning, whether you are supposed to show how to recognize that fact if it were not given, or how you are expected to use it. We really need you to tell us more!

It may be that you are expected to do nothing more than what you did: just list the terms in the sum that defines the 7th term, which ends with 7+4 = 11, and add them up: 1+1+2+3+4+5+6+7+8+9+10+11 = 67. Since that's what you said you did, and since the numbers are not large, I suspect that is all you had to do. You can do the same for part b, just calculating those terms (by adding 8+4 and 9+4, respectively, to terms you already have).

As you've seen, there are many more advanced ways to do this. We who know more than you do see the problem as calling for knowledge of recursive sequences, summation formulas, and so on, but clearly that is not what is expected of you. Those methods would be appropriate if they asked, say, for T₁₀₀₀. You are probably just learning the meaning of sequence notation, and a little about arithmetic progressions and the like. If you have learned the formula for the sum of an arithmetic progression, you could use that. But it isn't really necessary.

Can you please tell us what you are currently learning, so we can set these other ideas aside?

I'm just a form 5 students, so I'm only learning like basic concepts. So I don't really understand what is recursive sequences but I will insert what my teacher had taught me to do

 

[JeffM]

The problem is NOT that you are student in the fifth form. We are happy to work with students at any level.

The problem is that you did not give us any background about yourself, nor do you seem to have read the post entitled "Read before Posting." In this case, it resulted in a waste of time and effort because you got answers that were not appropriate to your level. There would have been some waste of time in any case because your book and teacher are using a term that is not generally used in the broader math community. Sometimes it takes a bit of dialogue before we can help. But understand that your being in the fifth form is fine by us.

 

[Wxlauslen123]

The problem is NOT that you are student in the fifth form. We are happy to work with students at any level.

The problem is that you did not give us any background about yourself, nor do you seem to have read the post entitled "Read before Posting." In this case, it resulted in a waste of time and effort because you got answers that were not appropriate to your level. There would have been some waste of time in any case because your book and teacher are using a term that is not generally used in the broader math community. Sometimes it takes a bit of dialogue before we can help. But understand that your being in the fifth form is fine by us.

Can you explain more what you meant by read before posting ? Do i need to insert a bit of background of my current studies along with the question ?

 

[JeffM]

When you went to the arithmetic forum, there was a list of posts to the left of your screen, the very first one says READ BEFORE POSTING. In the second post in this thread, you were asked to click on that post. Here is what you need to click on.

Read Before Posting

Welcome to FreeMathHelp.com! Please take the time to read the following before you make your first post. It will help you to get your math questions answered promptly and in the most helpful manner. Don't post a list of homework problems. Please start new threads for new exercises. Try to...

www.freemathhelp.com

It is not necessary to give any personal information, but it can help if you say what grade (form) you are in and what you are studying the first few times you post. That gives us a clue about what kind of answer to give you.

 

[Wxlauslen123]

When you went to the arithmetic forum, there was a list of posts to the left of your screen, the very first one says READ BEFORE POSTING. In the second post in this thread, you were asked to click on that post. Here is what you need to click on.

Read Before Posting

Welcome to FreeMathHelp.com! Please take the time to read the following before you make your first post. It will help you to get your math questions answered promptly and in the most helpful manner. Don't post a list of homework problems. Please start new threads for new exercises. Try to...

www.freemathhelp.com

It is not necessary to give any personal information, but it can help if you say what grade (form) you are in and what you are studying the first few times you post. That gives us a clue about what kind of answer to give you.

Alright , i get it now