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There are two Java Web Start tags:  : x 239 : x 320   Both tags refer to the same technology  refers to  both wiki point to  all questions tagged with  clearly relate to Java Web Start   I suggest they be merged into  (which appears in the auto-complete list if one types "webstart" in the Tags box when asking a new question). So i have this $3\times 3$ matrix  $$     \begin{pmatrix}     -2 &amp; 0 &amp; 0 \\     3 &amp; 1 &amp; -6 \\     0 &amp; 0 &amp; -2 \\     \end{pmatrix} $$  I want to check if the matrix is diagonizable. First thing i do is find the roots : namely $\lambda_1 = −2$ of multiplicity $2,$ and $\lambda_2 = 1$ of multiplicity $1.$  In order to ensure that the matrix is diagonalizable we need to find a basis of $\mathbb{R}^3$ whose elements are eigenvectors for $A.$ In particular, since we have the eigenvalue $\lambda_1=-2$ having multiplicity $2$ we need to check that the dimension of the eigenspace $E(\lambda_1)$ is equal to $2.$ We compute the eigenspaces of $A.$  $\DeclareMathOperator\Nul{Nul}$On the answer sheet is says that we need to find $\Nul(A+2Id)$... but why $2Id?$ Isn't is supposed to be $-2,$ so $\Nul(-2Id-A)$??   I do not understand this $\Nul(A+2Id).$ I always thought that we should compute $\Nul(-2Id-A),$ so what do i need to do ?   $\Nul(-2Id-A)$ gives me a different result from $\Nul(A+2Id).$  Does that mean that since $-2$ has a multiplicity of $2,$ we need to work with $2$ and not $-2$?  Somebody please help with a clear and simple explanation ! Thanks! Zooming in to inspect texture details in 3D view clips some closer faces like shown in the image. It's not the camera view so changing camera settings doesn't help.   Where can the distance to the clipping plane be adjusted? Send authors an inbox message if their question is closed I think it would really help if you get notified that a question of yours was closed.  Especially for the multi-site power user, usually (at least for me) a question is asked and then left alone for while. I rely on the network-wide inbox to tell me when someone has commented or answered, but if I don't receive any messages then I tend to assume that the question wasn't answered or even noticed. It's only when I check the question a day or two later to see what I can add do I find out it was closed.  This would be especially helpful for duplicates, where the answers you need are already there. A message to the effect of, "Closed as duplicate of question" is just like notifying me that a new answer has been added!  Unfortunately, question closures can remain unnoticed by their askers until months have passed. By then, the questions may either be too old to migrate to the correct site, or may , depending on the specific closing reason. We should notify users of these question closures so that they can improve them and learn from their mistakes.  Could closed questions get added to the inbox? Can a child enter the UK on an accompanied visa and then leave the country alone? E2099 Overflow in conversion or arithmetic operation Homology Groups of $S^n$ Book: Nanobot apocalypse on Earth, originally used for weather control I need to run something as sudo without a password, so I used visudo and added this to my sudoers file:  MYUSERNAME ALL = NOPASSWD: /path/to/my/program   Then I tried it out:  $ sudo /path/to/my/program [sudo] password for MYUSERNAME:    Why does it ask for a password? How can I run/use commands as root with a non-root user, without asking for a password? What are the technical advantages and disadvantages of mirrorless? The main doubt one can have about mirrorless is, I think that they do not provide ttl viewfinder. Is this a big disadvantage? In what way is it worst (or best) than classical reflex system?  What are the others advantages and disadvantages of a mirrorless compared to a reflex?  Have mirrorless a chance to replace reflex (at least for non pros) in the future? which adjective can I use to describe my neighbor, who is always trying to keep eye on my personal matters like what am I bringing from market or what am I cooking etc?  Regards, OS keyboard shortcuts conflict with apps keyboard shortcuts in GNOME 3 I have Ubuntu 16.04 with GNOME shell. I set ctrl+shift for the "Modifiers-only switch to next source" option.   This shortcut conflicts with apps hot-keys. I can't use ctrl+shift+i to open devtools in Chrome, it just switches the layout. In VS code IDE if I press shortcuts with ctrl+shift (for example ctrl+shift+f), shortcuts work but always switch a keyboard layout. When I used Windows this problem didn't exist.  Can I set the ctrl+shift shortcut in such a way that it causes a switch action only after the keys are released and only if this 2 keys were pressed (without additional keys)? Package in Java SEO for importing the page header with JavaScript rather than PHP My website has the same header/sidebar/footer on every page, so I have been importing them using PHP. To do this I forced all html files to be processed through the apache servers PHP handler via htaccess. I have come to understand that is not necessarily the best thing to do and so found out how to do everything I need using simple JavaScript. I also store a variable in the initial page that then gets used in the imported html.  Questions: By switching from:  &lt;?php include "_header.html";?&gt;   to  &lt;script type="text/javascript" src="_header.js"&gt;&lt;/script&gt;   I am noticing that the "view source" shows the header.js link, whereas the PHP method will show the source as if the html had been there all along. Will search engines recognize the html in the JavaScript just as they would when loaded with PHP?  I understand it is bad practice to alter the page contents -after- it is downloaded, but this doesn't fall into that category does it? That would detail things like after a wait function, or after user interaction, correct?  Are there any other foreseeable downfalls to switching to JavaScript and turning off the forced PHP processing? How to disable the skype ads (advertisement)? In D&amp;D 4E as with many RPGs, characters have a fixed armour value or AC. When attacking, the attacker must roll a die to overcome the target's AC. In 4E offensive magic works the same way: the target has a fixed Fortitude/Reflex/Will defence determined by their stats, and in order to hit, the attacker rolls to overcome whichever defence is relevant.   However it was not always like this. Some spells in 3E and now again in 5E work the opposite way. In those editions the target is the one who rolls against a fixed value determined by the caster's stats, in order to avoid spell-damage.  Both methods compare the attacker and target's stats, and have an element of randomness. I personally like the 4E system as it simplifies combat without leaving anything out. Why was the decision made, when designing the early D&amp;D editions (and still when iterating upwards into (A)D&amp;D 1e&ndash;3e), to use saving throws to control spells?  Answers should consist of designer quotes and not personal opinions. How do I view or install Ubuntu Touch apps? Lots of people have started developing Ubuntu Touch apps for the Ubuntu App Showdown and just in general, and have published them in the Click App Store.  What is the Click App Store, and how do I install apps published in it? Changing top, bottom, left & right margins on the fly I’m trying to find a way of being able to modify all of the margins of a page whenever I want to and as many times as I want to on a single page in order to be able to put text very easily where I want on a page.   I have thought of using the geometry package and using   \newgeometry{left=6.75cm, right=1cm, top=1cm, bottom=1cm}  %…  \restoregeometry   but unfortunately this only works for whole pages, so I can only change the margins once per page (and then they are valid for the whole page without having the possibility of changing them again).   I found the following script on the internet which enables users to change margins on the fly, just as I want to. The code below works fine and enables me to change the left and right margins of my page as many times as I want to, but unfortunately, it doesn’t give me the option of changing the top and bottom margins.  % placed before \begin{document}  \newenvironment{changemargin}[2]{% \begin{list}{}{% \setlength{\leftmargin}{#1}% \setlength{\rightmargin}{#2}% }% \item[]} {\end{list}}  % And then inside the document, whenever I want to use % the command to change the margins on the current page  \begin{changemargin}{1.9875cm}{-3.7625cm} % this means the left margin increases by 1.9875cm compared % to the default left margin (4.7625cm) (so left margin=6.75cm here) % and the right margin decreases by 3.7625cm (so right margin=1cm)  % ... (text or pictures in new environment)  \end{changemargin}   For this reason, I tried to adapt the code above and came up with the code below:  % placed before \begin{document} \newenvironment{changemargin}[3]{% \begin{list}{}{% \setlength{\leftmargin}{#1}% \setlength{\rightmargin}{#2}% \setlength{\topmargin}{#3}% }% \item[]} {\end{list}}  % And then to use the command: \begin{changemargin}{1.9875cm}{-3.7625cm}{1cm} % ... \end{changemargin}   It compiles and still changes the left and right margins but the top margin remains unchanged. (I haven’t yet tried to change the bottom margin).  Can anyone help me get this code to work completely, and enable me to modify the left, right, top and bottom margins of a page? Thanks. Prove that for all integers $n$, $n \geq 1$,   $$1 + 3 + 5 + \cdots + (2n - 1) = n\cdot n$$   How would I go about proving this? Is a general GRE score of X sufficient for entry to postgraduate degree Y?