I have on a few occasions in the past, downvoted a question and then after re-evaluation thought that it shouldn’t have been.  When trying to cancel the downvote or changing it to an upvote, I find that I cannot do that unless an edit is made.  Why is that?
I downvoted  and now really can't say why, so I wanted to remove my downvote. However, I get the message:  You last voted on this question yesterday Your vote is now locked in unless this question is edited  Why is this? I don't think I voted on it multiple times, and even when I did, I can change my mind, can't I?
Why does Li-Po battery voltage drop under load? I have very low background in electronics.  I have a Li-Po battery connected to an electric motor. The question is:   Why does battery voltage drop under load? Why is each cell of a Li-Po battery limited to 3.0 V (discharging)? Why is each cell of a Li-Po battery limited to 4.2 V (charging)? Proof of the Hockey-Stick Identity: $\sum\limits_{t=0}^n \binom tk = \binom{n+1}{k+1}$ After reading , the most popular answer use the identity $$\sum_{t=0}^n \binom{t}{k} = \binom{n+1}{k+1}.$$  What's the name of this identity? Is it the identity of the  modified.  How can we prove it? I tried by induction, but without success. Can we also prove it algebraically?  Thanks for your help.    EDIT 01 : This identity is known as the  because, on Pascal's triangle, when the addends represented in the summation and the sum itself are highlighted, a hockey-stick shape is revealed. How do I perform a Perl substitution on a string while keeping the original? Why don't the Ubuntu repositories have the latest versions of software? How can I explain to people that the phrase “off of ” is grammatically incorrect? How can I explain to people that the phrase off of is grammatically incorrect?  I‘ve heard this phrase used a lot, especially by Americans (though they aren't the only ones).    In my understanding, off of should usually be replaced by off, as in,     I took the book off the shelf   as opposed to     I took the book off of the shelf   Am I wrong?  Or is there perhaps some simple way I can explain this to most people? When I run followind command: qdbus I get following error:  qdbus: could not find a Qt installation of ''  I've read alot of old questions with same error but not one helps me.  I've tried execute following commands sudo apt-get install qt5-default + same for for qt4, etc. but still have same error.  If any additional information required for this issue - please add comment and I'll provide info. I want players to be able to click text to run an OP command even if that player is not an OP. For example something like:  Console: Do you want to enable Fly? [If you do, Please click here]  *Player1 clicks that text*  Console: /fly Player1   Is something like this possible? What is the largest positive $n$ for which $n^3+100$ is divisible by $n+10$  I tried to factorize $n^3+100$, but $100$ is not a perfect cube. I wish it were $1000$. If $[G' : G'']\leq p^2$, then $G'$ is abelian. Problem : Let $G$ be a p-group and $G'$ denote the commutator subgroup of $G$. If $[G' : G'']\leq p^2$, then $G'$ is abelian.  It is easy to prove it for the case of $[G' : G'']=1$ since G is solvable. But it is too hard to prove the other cases. Please give me any advice or solutions. Thanks in advance. I often read outputs in the terminal that get wrapped as they are too long. Since there is no way that I can modify the printed output, I need to let the Terminal allow for horizontal scrolling.  Is there a modification I can make to the default OS X Terminal to disable line wrapping and allow for horizontal scrolling?  Or do you know another alternative I can use? Where can I find the Ivory Claw to open a door in Reachwater Rock? I would like to ask a question about Java that doesn't have a specific answer. It's a question to see what people think and to share their opinion.    Will Stack Overflow tolerate this, or is there another Stack Exchange resource where I may ask a question like this? Mock a service while running a BrowserTest? I am trying to test the output of a controller that returns some information in a given page. This controller has a custom http client injected into it.  I want to create a BrowserTest that can navigate to a fake node, and then test for certain text or values. I also want to change the mock to return different values, so I can further test the output to account for those cases.  I tried:      $client = $this-&gt;getMockBuilder('\Drupal\mymodule\Client\AuthorizeClient')       -&gt;disableOriginalConstructor()       -&gt;getMock();     $client-&gt;expects($this-&gt;any())       -&gt;method('request')       -&gt;with('w12345', FALSE)       -&gt;willReturn([]);      $this-&gt;container-&gt;set('mymodule.auth_client', $client);   But I get errors in the test that refer to the original class, and not the one I am trying to replace. I looked around in the core but wasn't really able to find what I was looking for. Does it make sense to do this? Is there a way to do a Kernel test to test responses from the route in question? How do I make Units efficiently? I just blew almost all my money on a really cool lookin' ship. How do I regain solvency without spending a lot of time fiddling around in my inventory?  At the moment I've found a sequence of steps that'll turn 50 carbon and 100 Plutonium into ~5000 Units (by creating Suspension Fluid and then turning it into Electron Vapor). Are there better recipes or sequences of recipes I should look for? Or should I just drop the whole thing and go mine a particular mineral? Show $\sum\limits_{n=0}^{\infty}{2n \choose n}x^n=(1-4x)^{-1/2}$ How do you prove that $\sum\limits_{n=0}^{\infty}{2n \choose n}x^n=(1-4x)^{-1/2}$? I tried to identify the sum as a binomial series, but the $4$ and the $-1/2$ puzzle me. (This series arises in studying the first passage time of a simple random walk.) Equivalent of String.format in jQuery How do I set up new users with skel i have on my server a settings i use for all my users. every time i create a new user i have to copy all the settings over and over.  for example:   .vimrc. .profile .bashrc firefox homepage to our intranet evolution settings (server and username) etc...   i saw skel can do it, is there a easy way to setup a user with my settings when i adduser?  thanks Was Quirrell the Defense against the Dark Arts teacher for more than one year? It's well seen throughout the series that there is a “curse” on the DADA teacher position, that no one can hold that post for more than a year. But it seems like Quirrell has been around for longer than a year. What's up with that? Masking problems I am working with masking. Here is my node setting with the mask.   And here is my node settings  And what am i getting is this.    I tried invert node and many settings. It just doesnt work. Where am i going wrong I just watched a TV show and the guy says:     I ain't trying to fight with nobody with a baby.   So here, I can't understand the "nobody" since it make no sense to me, but it sounds like anybody, and if it's "I ain't trying to fight with anybody with a baby." that makes sense to me.