I am studying Unix and installed Ubuntu  but cannot update and I cannot solve, plz help me...  Problem  cannot update ubuntu18.10 by Err  What I did for solve  I know the artful does something wrong Searching some questions like this,  but I cannot find which line should be changed at all  deb http://archive.ubuntu.com/ubuntu artful main restricted$       6 # deb-src http://jp.archive.ubuntu.com/ubuntu/ artful main restricted$       7 $       8 ## Major bug fix updates produced after the final release of the$       9 ## distribution.$      10 deb http://archive.ubuntu.com/ubuntu artful-updates main restricted$      11 # deb-src http://jp.archive.ubuntu.com/ubuntu/ artful-updates main restricted$      12 $      13 ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu$      14 ## team. Also, please note that software in universe WILL NOT receive any$      15 ## review or updates from the Ubuntu security team.$      16 deb http://archive.ubuntu.com/ubuntu artful universe$      17 # deb-src http://jp.archive.ubuntu.com/ubuntu/ artful universe$      18 deb http://archive.ubuntu.com/ubuntu artful-updates universe$      19 # deb-src http://jp.archive.ubuntu.com/ubuntu/ artful-updates universe$   ()  could you explain me?  ERR MSG  E: The repository 'http://archive.ubuntu.com/ubuntu artful Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default.   E: The repository 'http://archive.ubuntu.com/ubuntu artful Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default.
Recently I have installed an older version of Ubuntu on my old machine. Whenever I try to install any software, I get an error saying it couldn't be found:  $ sudo apt-get install vlc Reading package lists... Done                Building dependency tree        Reading state information... Done     E: Couldn't find package vlc
How do I prove that $ \displaystyle\lim_{n \to{+}\infty}{\sqrt[n]{n!}}$ is infinite? How do I expire by type in .htaccess for remote loaded Google fonts? Is it possible to set expire by type for remote fonts or Google analytics? I'm getting this report from GTMetrix and everything I've tried isn't working. Suggestions?  There are 4 static components without a far-future expiration date. http://fonts.googleapis.com/css?family=Open+Sans:300 http://fonts.googleapis.com/css?family=Roboto&amp;subset=latin,latin-ext http://www.google-analytics.com/ga.js http://www.google-analytics.com/analytics.js   All of my other expires are working fine.  But apparently this type of thing isn't right?  ExpiresByType application/x-font-woff "access 1 year" ExpiresByType application/font-woff "access 1 year"   What should I do? Programmatically close aspx page from code behind What is the best way to close an ASPX page from the code-behind?    I have a button event handler that I want to close the page after the user has clicked an ASP.NET button on the page.  I have tried to programmatically add a JavaScript method that contains a window.close() command to the OnClientClick event to close the page but it does not work.  The button is also a asp:AsyncPostBoskTrigger for an AJAX Update Panel.  The application uses .NET Framework 3.5. Title bar settings missing in GNOME Tweaks on Ubuntu 20.04 I tried to move my "close, minimise and maximise" to the right + add the macOS theme to it. However, I have not been able to find any settings for that. In GNOME Tweaks > Windows the settings to put the buttons to the right are missing completely. How do I check to see if a text file is empty or does not exist in c++? Proving $\frac{x}{y} +\frac{y}{z} + \frac{z}{x} \ge 3$ for positive $x,y,z$ What makes SHA-256 secure? For example, RSA relies on a mathematically hard problem, factoring, while ECDSA or similar rely on discrete logarithm problem.  What makes SHA-256 and similar hash functions, of the same family, secure against pre-image and collision attacks? What's the math behind it? How to bake to vertex colors in blender cycles? I've had a very strange Finer error caused by recent macOS High Sierra betas that affected Macs running macOS 10.13 as well as macOS 10.12 Sierra. This error causes an entire Finder window to show visual artifacts when opening certain folders on either an APFS or HFS+ volume.  After moving the cursor or the affected Finder window, the window may look something like this;    Attempting to use Disk Utility to repair the affected volume does not resolve this issue, nor does restarting the affected Mac (even in Safe Mode).  Without formatting this disk, how can I prevent Finder from exhibiting this graphical error when opening particular folders? Limit $\frac{x^2y}{x^4+y^2}$ is found using polar coordinates but it is not supposed to exist. Consider the following 2-variable function:     $$f(x,y) = \frac{x^2y}{x^4+y^2}$$   I would like to find the limit of this function as $(x,y) \rightarrow (0,0)$.   I used polar coordinates instead of solving explicitly in $\mathbb R^2 $, and it went as the following:  $$ x = r \cos \theta, \qquad y = r\sin\theta $$   Hence,  $$\lim_{(x,y) \to (0,0)} \frac{x^2y}{x^4 + y^2} = \lim_{r \to 0}\frac{r^2\cos^2\theta(r\sin\theta)}{r^4\cos^4\theta + r^2\sin^2\theta}$$  This simplifies to,  $$ \lim_{r \to 0} \frac{r^3 \cos^2\theta\sin\theta}{r^2(r^2\cos^4\theta + \sin^2\theta)}$$  Simplifying $r^3/r^2$, we finally get;  $$\lim_{r \to 0} \frac{r (\cos^2\theta\sin\theta)}{r^2\cos^4\theta + \sin^2\theta}$$  Now from the above, we find that as $r \to 0$ the limit is $0$.   I wanted to verify this answer so I checked on Wolfram Alpha. Explicitly without changing to polar coordinates, it said that the limit does not exist at $(0,0)$ and rightly so. Then how is it that with polar coordinates, the limit exists and is $0$? Am I doing something wrong in this method?  Also, what should I do in this situation, and when should I NOT use polar coordinates to find limits of multi-variable functions? Someone edited my message on StackOverflow, but it really bugs me out.  I'm not sure what's wrong with it:   As you see, the bigger the circle becomes, the more vertices I need for hiding the straight lines. As you see, the bigger the circle becomes, the more vertices I need to hide the straight lines.   The latter (corrected) sentence just bugs me out for some reason. It would sound better if there was a comma after the word "need", perhaps, but I guess that would be even worse in means of grammatical correctness.  Can someone explain why is the first sentence bad and the second sentence correct? And could there even be better solution to fix the first sentence? C# Textreader and TextWriter are the another way to read and write file respectively...      I added a text box and button I called tbUpdate and btUpdate respectively...      In the right hand column, we’ll use three TextBlocks; the first and third as fixed labels (with the values Likeability: and % respectively)...      WorkerSupportsProgress and WorkerSupportsCancellation which hold true/false values that let the backgroundworker report progress or cancel an async progress respectively...   While learning many the many different aspects of development, I have not come across a book or series where the word respectively is not used in explaining an example. Honestly I guess it's implied that we know what it means. To me I always kind of skim over it because I can usually figure out what they're saying through the surrounding context. Can anyone explain this? Prove that ${\sqrt {n} }^{\sqrt {n+1}} > {\sqrt {n+1}}^{\sqrt {n}}$. Error installing Apache2 Server Copy over ssh and execute commands in one session Make OS X Terminal commands I type BOLD I'd like to make commands I've typed (input) into terminal stand out from all the output.   For example:  imac:~ buster$ chmod -R g-w myfolder  imac:~ buster$ cd myfolder imac:myfolder buster$ ls -l total 0 drwxr-xr-x   9 root  admin   306 Apr 20  2010 bin drwxr-xr-x   7 root  admin   238 Apr 20  2010 include drwxr-xr-x  73 root  admin  2482 May 18 17:16 lib drwxr-xr-x   6 root  admin   204 Apr 20  2010 man imac:myfolder buster$ echo Go Giants! Go Giants!  bold jumps to mind but I'd accept a color or even highlighting the whole line...   I'm sure there's a way to do this but it's not obvious to me...  thanks! What's the max height of blocks for a redstone contraption to still work even I'm in the surface below?  Like if I build a pillar to the max height of blocks and build a redstone contraption there, is it still going to work even I'm on the surface below? Replace \input{fileX} by the content of fileX automatically Algorithm to find Largest prime factor of a number What is the best approach to calculating the largest prime factor of a number?  I'm thinking the most efficient would be the following:   Find lowest prime number that divides cleanly Check if result of division is prime If not, find next lowest Go to 2.   I'm basing this assumption on it being easier to calculate the small prime factors. Is this about right? What other approaches should I look into?  Edit: I've now realised that my approach is futile if there are more than 2 prime factors in play, since step 2 fails when the result is a product of two other primes, therefore a recursive algorithm is needed.  Edit again: And now I've realised that this does still work, because the last found prime number has to be the highest one, therefore any further testing of the non-prime result from step 2 would result in a smaller prime. How to upload a file to a WCF Service? I've build a WCF Service to accept a file and write it to disk. The front-end consists of a page with SWFUpload which is handling the upload on the client side. Apparently, SWFUpload posts the data with a Content Type of: multipart/form-data.  I would think this ok but on the Service side I get an error. The error is "ProtocolException" expecting text/xml. I've tried different message encodings in the bindings but nothing seems to work.  How can I get this file uploaded using multipart/form-data?