Unifying descriptions for all tags across SE sites?
Why don't we add a question with the same tag on multiple Stack Exchange sites?
dpkg exit with error parsing file `/var/lib/dpkg/status`, what to do? If $\lim_{x\to\infty}(f(x)+f'(x))=L$ show that $\lim_{x\to\infty} f(x) = L$ and $\lim_{x\to\infty} f'(x) = 0$ Let $f:(0,\infty) \to R$ be differentiable. Suppose that $\lim_{x\to\infty}(f(x)+f'(x))=L$. Show that $\lim_{x\to\infty} f(x) = L$ and $\lim_{x\to\infty} f'(x) = 0$. (Hint: Write $f(x) = e^xf(x)/e^x$ and use l’Hopital’s Rule.)    My working for $\lim_{x\to\infty}f'(x)=0$:  For $\lim_{x\to\infty}f'(x) = 0$, I let $f(x) = e^xf(x)/e^x$ and applied quotient rule which then cancels off $e^{2x}$ and I'm left with $\lim_{x\to\infty}(f(x)+f'(x)-f(x))$. Can I then equate this with $\lim_{x\to\infty} \left(f(x)+f'(x)\right) - \lim_{x\to\infty}f(x)$ which then gives $L-L=0$? Is this step correct? How do I give text or an image a transparent background using CSS? Can I remove a digital signature from a DLL? Showing $\sup \{ \sin n \mid n\in \mathbb N \} =1$ Just read this which basically says you can freeze and thaw food in the fridge any number of times.    I'm still unclear on one point. If I had food which would be good in the fridge for 4 days and i put it in the freezer after 3 days, when I put it back in the fridge is my food good after its thawed for another 4 days or 1 more day? How to know add/edit page in hook_form_alter? I want to know whether form is add/edit in hook_form_alter. In Drupal 7 we can get all these in hook_form_alter.  I tried like this in D7:  function MYMODULE_form_alter(&amp;$form, &amp;$form_state, $form_id) {   // Check pages(s) , don't use $_GET.     if (strpos($form['#action'], '/add/') !== FALSE) {       $page = 'add';     }     if (strpos($form['#action'], '/edit') !== FALSE) {       $page = 'edit';     } }   Here I am getting add/edit in D7. Whereas in D8 I am not getting any it in $form['#actions']. And i don't want to use $_GET. Is there any way to check add/edit page in hook_form_alter. Find all solutions of the equality $y^2=x^3+23$ for integers $x,y$   I guess, that x cannot be even. because we can apply mod 4 test  say $x=2k$ then $y^2=8k^3+23\equiv3\mod(4)$   but, this is not possible, since the square of an integer is congruent to $0$ or $1$ $\mod (4)$  so $x$ is of the form $4k+3$ or $4k+1$  $x=4k+3$ is also not possible for the same reason but for the last case the test fails.  any hints ? Colors in Photoshop CS6/CC look different than in browser? One of my friends, a graphic designer told me recently that sometimes colors in Photshop look slightly different than the ones rendered in browser.  I know it is possible when you save a file and then use it on a website due to palettes, but he uses given color in PS, for example #b81e1e, then he creates a DOM element and sets its background to #b81e1e and the color is rendered differently in browser than in PS (I guess it's not that subtle as he can easily spot it). It's not a regular thing and it doesn't happen always, but he states it happened to him a few times, although he can't really tell me with witch colors.    Is it even possible? Because I have never really heard about anything like this &amp; nothing like this ever happened to me... Removing duplicate rows from table in Oracle I'm testing something in Oracle and populated a table with some sample data, but in the process I accidentally loaded duplicate records, so now I can't create a primary key using some of the columns.  How can I delete all duplicate rows and leave only one of them? sql server linked server to oracle returns no data found when data exists Why can Naruto still use Rasenshuriken? Automatic field should take the required entry KDB: apply dyadic function across two lists How much energy does lowering an object into a black hole generate? An object of mass m is slowly lowered into a black hole of mass 1000 m. Is the amount of braking energy larger than $0.6 mc^2$?   Now what if, after lowering the mass close to the event horizon, we wait the black hole to shrink to mass 100 m, by emitting Hawking radiation, and then we lower the mass some more? Is the braking energy of the second lowering process larger than $0.5 mc^2$?   I wonder can we extract more than $E=mc^2$ energy from mass m?  (In this thought experiment we use a wire and a winch, or anything that works) My Linux Mint 15 install on VirtualBox was working great up until about two days ago, when the updater started throwing a ton of errors and refuses to progress with any apt-get update, apt-get install, or apt-get upgrade.  They are 404 errors on the archive.ubuntu.com site, under the /ubuntu/dists/raring-updates folder. I looked at it, it doesn't exist.  a direct link, which shows there is no raring-updates.  Where has raring-updates gone and what can I do to fix this? What is the difference between topological and metric spaces? What is the difference between a topological and a metric space? Does this double sum $\sum_{m=0}^\infty \sum_{n=0}^\infty \frac{m+n+mn}{2^m(2^m+2^n)}$ converge? How can I prove the Carmichael theorem I am trying to prove that these two definitions of Carmichael function are equivalent.  I am using this definition of Carmichael function:     $\lambda(n)$ is the smallest integer  such that $k^{\lambda(n)}\equiv1 \pmod n\,$ $\forall  k$ such that $\gcd(k,n)=1$.   to prove this one:     $\lambda(n) = \begin{cases}\phi(p^a) &amp; (p=2\text{ and }a\le 2)\text{ or }(p\ge 3)\\\dfrac 1 2 \phi{(2^a)}  &amp; a\ge 3\\ \text{lcm}\left((\lambda(p_1^{a_1}),\cdots,\lambda(p_k^{a_k})\right)&amp; \text{for }n=\prod_{i=1}^k p_i^{a_i} \end{cases}$   Since $a^{\lambda(n)}\equiv 1 \pmod n$,  and $a^{\lambda(m)}\equiv1 \pmod m$ with $\gcd(m,n)=1 \implies a^{\text{lcm}({\lambda(n)},\lambda(m)}\equiv1 \pmod {nm} $   Hence $\lambda (mn)=\text{lcm}(\lambda(n), \lambda(n))$ for $m$ and $n$ coprime to each other.  How can I prove the other relations? Safely turning a JSON string into an object Given a string of JSON data, how can I safely turn that string into a JavaScript object?  Obviously I can do this unsafely with something like:  var obj = eval("(" + json + ')');   but that leaves me vulnerable to the JSON string containing other code, which it seems very dangerous to simply eval.