When I want to watch a question the content disappear.          App Version: 1.0.85 Device Manufacturer: samsung Device Model: SM-G920F OS Version: 6.0.1 (G920FXXU3DPCM)
Since the last update (v1.0.85), I am getting all the question pages blank on the Android app. For those who are confused with the image, I'm using RtL (Right-to-Left) layout.        If I scroll down (quite a bit) I can see the question. But even then I cannot see the question title, the related comments or answers.         App Version: 1.0.85 Device Manufacturer: LGE Device Model: LG-D620   OS Version: 5.0.2 (152541901f156)
In the decimal system: $...-3, -2, -1, 0, 1, 2, 3...$ In the binary system: $...-11, -10, -1, 0, 1, 10, 11...$ In the unary system: $-111, -11, -1, \text{ ??? }, 1, 11, 111...$   I was only able to find a related question but none with an answer so far: I can think of several examples of functions such that twice application of the function is equivalent to no application of it.   Additive inverse Multiplicative inverse Fourier transform Complex conjugation Any group built up from $\mathbb{Z}_2$, applying (one of) the $\mathbb{Z}_2$ parts' operation.   "Idempotent" came to mind, but that's wrong. It means $f(f(x)) = f(x)$, not $f(f(x))=x$.  What is the word for this "flip-flop" property? How to Deserialize XML document Irreducible cyclotomic polynomial Why don't we consider centrifugal force on a mass placed on earth? Let us say a block of mass is placed on the surface of earth. Then while drawing the forces on that body, we say:   Force $F = mg$ acting towards the center of Earth. Normal reaction $N$ offered by the surface of Earth.   If no other forces are acting, we say $F=N$. But what about the centrifugal force $m\omega^2R$ . Why don't we ever bring that into picture? What am I missing? To show that $2$ | $x^{2n} - x^n$, $n \in \mathbb{Z^+}$ is the following adequate? Show that $2$ | $x^{2n} - x^n$, $n \in \mathbb{Z^+}$   Let $x^n = a$ then $\frac{a}{2}$ $\implies a = 2q + r$ such that $r = 0 \vee r = 1$.   So $x^{2n} = (x^n)^2 = a^2 = (2q + r)^2$, which means that $2|[x^{2n} - x^n ]= 2| [(2q + r)^2 - (2q + r)]$. If $r = 1$ we get $(4q^2 + 4q + 1) - 2q - 1 = 4q^2 + 2q = 2(2q^2 +1)$. Thus $2$|$x^{2n} - x^n$, $n \in \mathbb{Z^+}$. Is this reasoning correct? Is it adequate? Is every dense subspace of a separable space separable? The question says to solve this equation: $(z+1)^5 = z^5$  I did. Just want to find out if I did it properly and if my run-around logic makes sense.  First I begin my writing the equations as:  $$ (z+1)^5 = z^5$$ $$ \mathbf{e}^{5 \mathbf{Log}(z+1)} = \mathbf{e}^{5 \mathbf{Log}(z)} $$ So $$  \mathbf{Log}(z+1) = \ln|z+1| + \mathbf{Arg}(z+1)i $$   $$  \mathbf{Log}(z) = \ln|z| + \mathbf{Arg}(z)i $$   Now, because the natural logarithm is one-to-one, I write:  $$ \ln |z| = \ln |z+1| \Rightarrow |z| = |z+1|$$   So assign $ z = a +bi$   So that $|z| = \sqrt{a^2 +b^2} = |z+1| = \sqrt{(a+1)^2 +b^2} \Rightarrow a^2 +b^2 = (a+1)^2 +b^2 \Rightarrow a^2 = (a+1)^2 \Rightarrow a = -\frac12 $  So, $z = -\frac12 + bi$ and $z+1 = \frac12 + bi$ for some $b \in \mathbb R$  Now to find $b$  $$ \mathbf{Arg}(z+1) = \mathbf{Arg}(z)$$ $$ \tan^{-1} \frac{b}{\frac12} = \pi - \tan^{-1}\frac{b}{-\frac12}$$  I have a feeling this last part isn't quite right, so I just want to find out if I'm approaching this question properly?  Ultimately, I get $ z = -\frac12$ which upon inspection...is wrong... I have just bought a new computer and I have everything migrated over except for my Steam games.  I looked in Program Files/Steam/ and I found a folder full of the games I have downloaded, but I do not know if it is safe to just copy these folders from one computer to another (seeing as a lot of other applications will not work if you do this), or is there another recommended way?  I don't really feel like re-downloading all my games. I don't have the time nor bandwidth to download 20GB over a 1.5mbps connection.  Is it possible to contact Valve and get a disk with the games on it? Change all file type associations from one program to another 14.04.5 to 16.04 Update failed - xenial.tar.gz.gpg missing The update from Trusty to Xenial is officially available via the software updater. After updating all packages, upgrading through the software updater yields:  Fetching the upgrade failed. There may be a network problem.   Doing a sudo do-release-upgrade yields:      Checking for a new Ubuntu release Err Upgrade tool signature                                                        403  Sorry, not allowed to fetch that type of file: xenial.tar.gz.gpg         Err Upgrade tool                                                                  403  Sorry, not allowed to fetch that type of file: xenial.tar.gz             Fetched 0 B in 0s (0 B/s)                                                       WARNING:root:file 'xenial.tar.gz.gpg' missing Failed to fetch Fetching the upgrade failed. There may be a network problem. Using Fingerprint reader in 16.04 I have a Dell laptop with fingerprint reader inbuilt. I just ran lsusb on terminal and got the following result:   Bus 002 Device 003: ID 138a:0011 Validity Sensors, Inc. VFS5011 Fingerprint Reader Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub Bus 003 Device 002: ID 046d:c077 Logitech, Inc. M105 Optical Mouse Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 001 Device 004: ID 05ca:1820 Ricoh Co., Ltd Integrated Webcam Bus 001 Device 003: ID 0a5c:21bc Broadcom Corp. BCM2070 Bluetooth 2.1 + EDR Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub   Is it possible to use fingerprint scanning instead of traditional login with 16.04 and Unity ? Thanks. ColdFusion adding extra quotes when constructing database queries in strings I am coding in ColdFusion, but trying to stay in cfscript, so I have a function that allows me to pass in a query to run it with   &lt;cfquery blah >   #query# &lt;/cfquery>   Somehow though, when I construct my queries with sql = "SELECT * FROM a WHERE b='#c#'"  and pass it in, ColdFusion has replaced the single quotes with 2 single quotes.  so it becomes  WHERE b=''c'' in the final query.  I have tried creating the strings a lot of different ways, but I cannot get it to leave just one quote.  Even doing a string replace has no effect.   Any idea why this is happening?  It is ruining my hopes of living in cfscript for the duration of this project Make mod_wsgi use python2.7.2 instead of python2.6? i am running Ubuntu 10.04.1 LTS  and it came pre-packed with python2.6 but i need to replace it with python2.7.2.   (The reason is simple, 2.7 has a lot of features backported from 3 )  i had installed python2.7.2 using  ./configure make make altinstall   the altinstall option installed it, without touching the system default version, to /usr/local/lib/python2.7 and placed the interpreter in /usr/local/bin/python2.7  Then to help mod_wsgi find python2.7 i added the following to /etc/apache2/sites-available/wsgisite  WSGIPythonHome /usr/local   i start apache and run a test wsgi app BUT i am greeted by python 2.6.5  and not Python2.7  Later i replaced the default python simlink to point to python 2.7  ln -f /usr/local/bin/python2.7 /usr/bin/python   Now typing 'python' on the console opens python2.7 but somehow mod_wsgi still picks up python2.6  Next i tried,  PATH=/usr/local/bin:$PATH export PATH   then do a quick restart apache, but yet again its python2.6 !!    Here is my $PATH  /usr/local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games   contents of /etc/apache2/sites-available/wsgisite  WSGIPythonHome /usr/local   &lt;VirtualHost *:80&gt;      ServerName wsgitest.local     DocumentRoot /home/wwwhost/pydocs/wsgi     &lt;Directory /home/wwwhost/pydocs/wsgi&gt;         Order allow,deny         Allow from all     &lt;/Directory&gt;      WSGIScriptAlias / /home/wwwhost/pydocs/wsgi/app.wsgi  &lt;/VirtualHost&gt;   app.wsgi  import sys  def application(environ, start_response):     status = '200 OK'     output = sys.version      response_headers = [('Content-type', 'text/plain'),                         ('Content-Length', str(len(output)))]     start_response(status, response_headers)      return [output]   Apache error.log  'import site' failed; use -v for traceback [Sun Jun 19 00:27:21 2011] [info] mod_wsgi (pid=23235): Initializing Python. [Sun Jun 19 00:27:21 2011] [notice] Apache/2.2.14 (Ubuntu) mod_wsgi/2.8 Python/2.6.5 configured -- resuming normal operations [Sun Jun 19 00:27:21 2011] [info] Server built: Nov 18 2010 21:20:56 [Sun Jun 19 00:27:21 2011] [info] mod_wsgi (pid=23238): Attach interpreter ''. [Sun Jun 19 00:27:21 2011] [info] mod_wsgi (pid=23239): Attach interpreter ''. [Sun Jun 19 00:27:31 2011] [info] mod_wsgi (pid=23238): Create interpreter 'wsgitest.local|'. [Sun Jun 19 00:27:31 2011] [info] [client 192.168.1.205] mod_wsgi (pid=23238, process='', application='wsgitest.local|'): Loading WSGI script '/home/wwwhost/pydocs/$ [Sun Jun 19 00:27:50 2011] [info] mod_wsgi (pid=23239): Create interpreter 'wsgitest.local|'.   Has anybody ever managed to make mod_wsgi run on a non-system default version of python ? Some irreducible character separates elements in different conjugacy classes Let $x$ and $y$ be elements that are not conjugate in $G$.  Then there is some irreducible character $\chi$ such that $\chi(x) \not = \chi(y)$.   Clearly the "irreducible" part isn't important, since any character can be written as the sum of irreducible characters, but I'm having trouble going beyond that.  I'd appreciate a good hint over a full answer, and I'd be most interested in a way to construct a group representation $\varphi:G \to GL(V)$ of $G$ such that the character of the representation takes different values on $x$ and $y$. Why isn't Google Chrome available in the Software Centre? When is $2^n \pm 1$ a perfect power Is there an easy way of showing that $2^n \pm 1$ is never a perfect power, except for $2^3 + 1 = 3^2 $?  I know that   gives the result directly, but I'm hopefully for a more elementary method.    I can show that it is never a square, except for $2^3 + 1$.  Proof: Cases $n=1, 2, 3$ are easily dealt with. Henceforth, let $n\geq4$.  $2^n -1 \equiv 3 \pmod{4}$ hence is never a square.     If $2^n +1 =x^2$, then $2^n = (x-1)(x+1)$ and both of these are powers of 2. Thus we must have $(x-1) = 2, (x+1) = 4$. This gives the solution of $2^3 + 1 = 3^2$.    Let's now do an odd prime.  Say $2^n +1 = x^p$. Then $2^n = x^p - 1 = (x-1)(x^{p-1}+x^{p-2} + \ldots +1)$, so both terms are powers of 2. We have $ x = 2^m+1$ is odd. But the other term is the sum of $p$ odd numbers, hence is odd. Since this is clearly greater than 1, we get a contradiction.  Say $2^n -1 = x^p$. Then $2^n = x^p + 1 = (x+1)(x^{p-1} - x^{p-2} + \ldots -x +1 )$, so both terms are powers of 2. We have $x = 2^m -1$ is odd. But the other term is the sum of $p$ odd numbers, hence is odd. Since $x^p + 1 \neq x+1$ except for $p=1$, this means that the term is greater than 1. Hence we get a contradiction. Saving Mathematica kernel state? Why does the series $\sum_{n=1}^\infty\frac1n$ not converge? Calculate the area of an irregular cyclic convex polygon