Sequence formula [itex]a_{n}[/itex]=((last term) - (n-1)(common diff))


by Lebombo
Tags: anlast, diff, formula, n1common, sequence, term
Lebombo
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#1
Apr17-13, 08:31 PM
P: 135
Calc 2 will require some basic knowledge of sequences and series. Since this topic has never been covered in any of my past math classes, I am currently learning about sequences and series from scratch. On youtube, I found a video that contains an explanation of the General Term of the Arithmetic Sequence formula. It also contains another form which does not exist in my Algebra Textbook:

[itex]a_{n}[/itex] = ((last term) - (n-1)(common diff))

However, I think the person providing the youtube explanation makes a mistake in notation, which is causing me some confusion. If he has written this portion of his presentation correctly, then I will have to go back and review my confusion. So if anyone has a moment, could you fact check the portion of the derivation of this formula at exactly 9:16 - 9:23

http://www.youtube.com/watch?v=dbuwv...BFE1A5A41BC8D6

To me it seems [tex]a_{n}- a_{n-1} [/tex] should equal d, not -d , so did he intend to write [tex]a_{n} - a_{n+1} = -d[/tex]
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ArcanaNoir
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#2
Apr18-13, 10:37 AM
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P: 753
Yes this is a mistake. I think he meant to have [itex] a_n-a_{n+1}=-d [/itex]

I watched the video but I didn't listen to it because I'm in class.


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