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# I think its impossible watch

1. Me amd a frind have spent an hour on this as question and im about to gube up because we hsve gotten NOWHERE please can someone explain 2(ii)
2. (Original post by Saffronwillow)
Me amd a frind have spent an hour on this as question and im about to gube up because we hsve gotten NOWHERE please can someone explain 2(ii)
Note that what you have is an arithmetic sequence with common difference -3 and first term 102.

Now you know the formula for the sum of the first n terms of an arithmetic sequence, don't you?
3. (Original post by Zacken)
Note that what you have is an arithmetic sequence with common difference -3 and first term 102.

Now you know the formula for the sum of the first n terms of an arithmetic sequence, don't you?
Yeah its 102+99+96=297
4. (Original post by Saffronwillow)
Yeah its 102+99+96=297
Huh? The sum to n terms is given by . Just plug in and .

For the value for which the sum if zero, just set the equation to 0 and solve for , ignoring non-positive solutions.
5. (Original post by Zacken)
Huh? The sum to n terms is given by . Just plug in and .

For the value for which the sum if zero, just set the equation to 0 and solve for , ignoring non-positive solutions.
Oooh, THANK YOU

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