- #1

- 27

- 0

n

[tex]\Sigma[/tex] (i

^{2}-3)

i=3

If i was equal to 1 I would be able to solve this, but I'm not sure what to do since it is equal to 3.

Thanks!

- Thread starter haydn
- Start date

- #1

- 27

- 0

n

[tex]\Sigma[/tex] (i

i=3

If i was equal to 1 I would be able to solve this, but I'm not sure what to do since it is equal to 3.

Thanks!

- #2

symbolipoint

Homework Helper

Education Advisor

Gold Member

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- 1,152

If you shift the initial index from 3 to 1, then you need to change the general term the same number of index units in the other direction. That is how you compensate for the change to the index variable.

I'm searching for the proper latex formatting in this message tool set but cant' find it.

Summation from 3-2 to n, of (i+(3-1))

You know you wanted to change the starting index value by 2 units to the left, so you change the general term by 2 units to the right.

- #3

symbolipoint

Homework Helper

Education Advisor

Gold Member

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I just need to try this:

[tex]^{n}_{1}[/tex][tex]\sum[/tex](i+2)^{2}-3

Not exactly the way I hoped it would look, but it is very close; maybe readable by understanding reading members.

[tex]^{n}_{1}[/tex][tex]\sum[/tex](i+2)

Not exactly the way I hoped it would look, but it is very close; maybe readable by understanding reading members.

Last edited:

- #4

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- 0

Think about it, if we have

n

[tex]\Sigma[/tex] (i^{2}-3)

i=3

If i was equal to 1 I would be able to solve this, but I'm not sure what to do since it is equal to 3.

Thanks!

[tex] \sum_{i=1}^{n} i^{2} - 3 [/tex]

Now let's write out the first term, we now have

[tex]\sum_{i=1}^{n} i^{2} - 3 = (1^{2} - 3) + \sum_{i=2}^{n} i^{2} - 3 = -2 + \sum_{i=2}^{n} i^{2} - 3 [/tex]

Keep writing out the terms until you get to your sum i.e. the one that starts from 3.

Do you see what the answer is?

- #5

HallsofIvy

Science Advisor

Homework Helper

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i

n

[tex]\Sigma[/tex] (i^{2}-3)

i=3

If i was equal to 1 I would be able to solve this, but I'm not sure what to do since it is equal to 3.

Thanks!

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