Timeline for How can I get simplified answer for SUM?
Current License: CC BY-SA 4.0
15 events
| when toggle format | what | by | license | comment | |
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| S Oct 18, 2022 at 20:14 | history | suggested | Glorfindel | CC BY-SA 4.0 |
typos corrected
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| Oct 18, 2022 at 19:30 | review | Suggested edits | |||
| S Oct 18, 2022 at 20:14 | |||||
| Sep 22, 2022 at 3:01 | history | tweeted | twitter.com/StackMma/status/1572783069832290304 | ||
| Sep 21, 2022 at 23:21 | history | became hot network question | |||
| Sep 21, 2022 at 19:38 | vote | accept | Azzurro94 | ||
| Sep 21, 2022 at 18:44 | history | edited | Azzurro94 | CC BY-SA 4.0 |
added 10 characters in body
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| Sep 21, 2022 at 18:38 | history | edited | Azzurro94 | CC BY-SA 4.0 |
added 373 characters in body
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| Sep 21, 2022 at 18:02 | vote | accept | Azzurro94 | ||
| Sep 21, 2022 at 18:38 | |||||
| Sep 21, 2022 at 17:59 | answer | added | userrandrand | timeline score: 2 | |
| Sep 21, 2022 at 17:18 | comment | added | Azzurro94 | @DanielHuber thanks. you are right but I need something like generic, symbolic one. | |
| Sep 21, 2022 at 17:17 | comment | added | Daniel Huber | If you give k a definite values, you get ar[1] | |
| Sep 21, 2022 at 17:17 | answer | added | Bob Hanlon | timeline score: 6 | |
| Sep 21, 2022 at 17:09 | comment | added | userrandrand |
Not a general solution but for the example you gave you could use Sum[ar[j], { j, 1, k}] + Sum[- ar[j], { j, 2, k}] /. Sum[-a_, b_] :> - Sum[a, b] /. Sum[a_, {b1_, b2_, b3_}] :> Sum[a, {b1, 1, b3}] - Sum[a, {b1, 1, b2 - 1}]. That replacement rule uses Sum[ar[j], {j, 1, 0}]=0 in the first sum of your example.
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| Sep 21, 2022 at 16:30 | comment | added | Bill |
I believe you will find that Mathematica does not automatically take Sums apart. I am guessing that is because of the many strange things that can happen when k turns out to be infinite and/or some of ar[j] turn out to be infinite or undefined or ... Think of the most malicious sums, things REALLY evil, and imagine what those borderline cases might do to a relatively mindless piece of software trying to follow a vast list of generic rules
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| Sep 21, 2022 at 15:21 | history | asked | Azzurro94 | CC BY-SA 4.0 |