I recently did a fresh installation of Ubuntu 13.10; but there is something bothering me, which I don't quite understand.   When I first tried to toggle the keyboard language(I usually switch between Persian and English) using the good old "Alt+Shift" shortcut it didn't work. Then, I went and checked the Keyboard shortcut settings and found out that it had been set to "Super+Space"(which BTW didn't work either). So I tried to change it back to "Alt+Shift" but it just doesn't work; when I press "Alt+Shift" to set it up as the toggle-language shortcut, the box automatically resets itself to its previous value(without any errors whatsoever). As far as I've checked I couldn't find any thing obvious corresponding to the shortcut "Alt+Shift" either.  I've currently set up the shortcut as "Ctrl+Space"; so I can toggle the language. My question is why I cannot set it up to just "Alt+Shift"?
I recently upgraded to Ubuntu 13.10, with the new keyboard handling system. The little "switch keyboard" option does not let me set it to Alt+Shift. How can I get this keyboard binding, as I have absolutely no interest in using the Mac-esque Super+Space combo?
Prove the Radical of an Ideal is an Ideal I am given that $R$ is a commutative ring, $A$ is an ideal of $R$, and $N(A)=\{x\in R\,|\,x^n\in A$ for some $n\}$.  I am studying with a group for our comprehensive exam and this problem has us stuck for two reasons.  FIRST - We decided to assume $n\in\mathbb{Z}^+$ even though this restriction was not given. We decided $n\ne 0$ because then $x^0=1$ and we are not guaranteed unity. We also decided $n\notin\mathbb{Z}^-$ because $x^{-1}$ has no meaning if there are no multiplicative inverses. Is this a valid argument?  SECOND - We want to assume $x,\,y\in N(A)$ which means $x^m,\,y^n\in A$ and use the binomial theorem to expand $(x-y)^n$ which we have already proved is valid in a commutative ring and show that each term is in A so $x-y$ is in $N(A)$. The biggest problem is how to approach the $-y$ if we are not guaranteed unity. Does anyone have any suggestions?  Thank you in advance for any insight. Discriminant analysis vs logistic regression I found some pros of discriminant analysis and I've got questions about them. So:     When the classes are well-separated, the parameter estimates for   logistic regression are surprisingly unstable. Coefficients may go to   infinity. LDA doesn't suffer from this problem.      If number of features is small and the distribution of the predictors   $X$ is approximately normal in each of the classes, the linear   discriminant model is again more stable than the logistic regression   model.    What is stability and why is it important? (If logistic regression provides a good fit that does its job, then why should I care about stability?)      LDA is popular when we have more than two response classes, because it   also provides low-dimensional views of the data.    I just don't understand that. How does LDA provide low-dimensional views? If you can name more pros or cons, that would be nice. Select Input Texture file name as parameter/node How to return to the GUI? I am very new to Linux and Ubuntu. I use Ubuntu 11.10.  I was trying to exit the X server (in order to install some Nvidia drivers) and I typed in the terminal:  sudo service lightdm stop   How can I return to the Ubuntu interface? Showing that $\int\limits_{-a}^a \frac{f(x)}{1+e^{x}} \mathrm dx = \int\limits_0^a f(x) \mathrm dx$, when $f$ is even I have a question:     Suppose $f$ is continuous and even on $[-a,a]$, $a&gt;0$ then prove that   $$\int\limits_{-a}^a \frac{f(x)}{1+e^{x}} \mathrm dx = \int\limits_0^a f(x) \mathrm dx$$   How can I do this? Don't know how to start. Method defined as testMethod do not support web service callouts, test skipped I have been struggling with this error for a few days now. I get this error every time I try to run a test for a method that has an httpCallout. I followed the architecture from  , but to no avail. I thought it could be something I was messing up in my code, so I copied all three of the classes from the documentation, and I am still getting the error when I try to run the test. All of the classes are on Salesforce API 29. Has anyone run into this before? Yesterday, I have received two : Revival, and Self-Learner. However I was only notified of the Revival badge, because apparently the Self-Learner badge is not considered "".  What badges have their notification suppressed if the user has a 200-rep account somewhere on the Stack Exchange network, i.e. they won't trigger a new item in our achievements dialog? When did the red shirt careers change to yellow shirts in Star Trek and why? No Drupal Site Found when clearing cache I installed drush using composer following the instructions here:   When trying to run drush cc all I get this error:     No Drupal site found, only 'drush' cache was cleared.[warning] 'all'   cache was cleared. [success]   I added this line:  export PATH="/Applications/MAMP/bin/php/php5.6.2/bin:$PATH"   to my .bash_profile and restarted bash and MAMP. Still no luck. Any ideas?   This is my drush status:   Drupal version         :  7.36                                                               Site URI               :  http://default                                                     Database driver        :  mysql                                                              Database hostname      :  localhost                                                          Database port          :                                                                     Database username      :  root                                                               Database name          :  srod                                                     PHP executable         :  /usr/bin/php                                                       PHP configuration      :                                                                     PHP OS                 :  Darwin                                                             Drush script           :  /Users/srod/.composer/vendor/drush/drush/drush.php   Drush version          :  7.0-dev                                                            Drush temp directory   :  /tmp                                                               Drush configuration    :                                                                     Drush alias files      :                                                                     Drupal root            :  /Applications/MAMP/htdocs/srodsite                             Site path              :  sites/default      I'm running it from Drupal project folder. I am a new user, who has just been told to run / execute a command. The answer has some text with a grey background like this text here or  sometimes this text here.   However, I don't know what "run" or "command" means in relation to Ubuntu.  How do I do this?    This is intended for use as a Q&amp;A you can link to when you tell someone to run a command. What is the default root password? Closing as "off topic" has just gotten painful I know that useability and friendliness are given priority in the features implemented on StackExchange, but after using the new close-as-off-topic flow for the first time I would have to say I'm somewhat underwhelmed.  Why do we not have a simple It's off topic type reason? And why do I have to write half a book chapter as my custom close reason, especially when I can go back and edit the automatically posted comment so that it's way shorter?   This question complaint is prompted by  here on Meta. It's off topic, plain and simple. We now have a bunch of people wanting to close it, all potentially writing their own custom close reasons, it's just messy suboptimal. Regardless of how nice and friendly you want to be to the user, this particular question shouldn't need an explanation.    Does the off topic flow have to stay this way? Can we allow higher rep users to close as off topic without having to specify a (really long) custom reason, maybe have some canned reasons like we used to?  Edit: just to be clear, there are still three canned close reasons, but none of them were applicable to this example. The second one is closest, but does not appear to seek input... is quite different to It's a question, but doesn't belong here in any way, shape, or form. How to show  tag literally in / tag? How to get my own IP address and save it to a variable in a shell script? How can I get my own IP address and save it to a variable in a shell script? Selenium + FF : How to fix error, Unable to connect to host 127.0.0.1 on port 7055 after 45000 ms? How to read high voltages on microcontroller? Which is the preferred way to convert an Enum to a String in .NET 3.5?   Enum.GetName Enum.Format ToString   Why should I prefer one of these over the others? Does one perform better? What are the options for traveling to the airports in Paris? How to solder with one hand? I am a beginner at electronics.  I don't have many tools and stuff, so I am forced to solder by hand.   I don't have a pcb to solder on, so I usually just solder the wires together, but it's really difficult without a holder.  Is there an easier way to do this? If not, is there a substitute for a wire holder?  Any help would be appreciated. Fermat primes relation to $2^n+1$ If $2^n+1$ is prime how to show that  $n$ must be a power of $2$  Being at elementary level I am at a loss what to begin with?