Git unable to push to git repository
Git SSH error: "Connect to host: Bad file number"
How to specify the SMTP server in PHPMailer? Is there any method to close connection similar to  for  in WordPress?  Is it not necessary to close connection for global $wpdb? Preventing itemize environment to insert initial vertical space Intersection of two parabolae Problem: Consider two parabolae such that their axes of symmetry form a right angle. Prove that all four points of intersection lie on a common circle (it is an assumption that there exist such four points). Could you help me obtain a non-algebraic solution? (The algebraic one I did is given below.)  Algebraic solution:  There is a very simple algebraic approach, just introduce a Cartesian coordinate system such that the parabolae are given by equations:  $$y = \alpha_1 x^2 + \beta_1 $$ $$x = \alpha_2 y^2 + \beta_2 $$  and by scaling, adding and simplifying we can get the following ordinary circle equation (the right-hand side is positive because parabolae intersect): $$ \left(x-\frac{1}{2\alpha_2}\right)^2 + \left(y - \frac{1}{2\alpha_1}\right)^2 = \frac{-\beta_1}{\alpha_1} + \frac{-\beta_2}{\alpha_2} + \left(\frac{1}{2\alpha_1}\right)^2 + \left(\frac{1}{2\alpha_2}\right)^2$$  Non-algebraic solution: ?? Getting error message when trying to start a virtual machine I have been using VMWare on Windows for a long time. But after a long wait, I moved to VirtualBox on Ubuntu 11.10. I installed Ubuntu, 32 Bit, installed all available updates and installed Virtual Box. When I try to create a new Windows installation inside VirtualBox, I got the following error messages.  VirtualBox - Error  Failed to open a session for the virtual machine Windows XP. The virtual machine '**Windows XP**' has terminated unexpectedly during startup with exit code 1. Details  Result Code: NS_ERROR_FAILURE (0x80004005) Component: Machine Interface: IMachine {5eaa9319-62fc-4b0a-843c-0cb1940f8a91}   2nd error dialogue  Virtualbox - Error in suplibOsinit Kernal driver not installed (rc--1908) Please install the virtualbox-dkmbs package and execute 'modprobe vboxdrv' as root.    I have already tried reinstalling VirtualBox. Google result seem to indicate the the problem happens due to Kernel updates.   Is there anyway I can get this working? I need this for malware analysis and if VirtualBox is going to crash on me all the time, then I won't be able to use Ubuntu for work.  Output to dpkg -l | grep virtual   server rc  virtualbox                             4.1.2-dfsg-1ubuntu1                     x86 virtualization solution - base binaries rc  virtualbox-qt                          4.1.2-dfsg-1ubuntu1                     x86 virtualization solution - Qt based user interface  cute 'modprobe vboxdrv' as root.&lt;p&gt; How do I make a redirect in PHP? To prove the limit of $\frac{x^2+2\cos x-2}{x\sin^3 x}$ at zero is $1/12$ Fubini's theorem for series with dependent indices As a part of a proposition about power series that I am trying to prove I have to show that  $$ \sum_{m=0}^{\infty} \left(\sum_{n=m}^{\infty} \frac{n!}{m!(n-m)!}(b-a)^{n-m}c_n\right)(x-b)^m = \sum_{n=0}^{\infty}c_n(x-a)^n$$  Proof: What I have done so far is to show that  $$\sum_{m=0}^{n} \frac{n!}{m!(n-m)!}(b-a)^{n-m}(x-b)^m = (x-a)^n $$  So the next idea is to use Fubini's rearrangement theorem for infinite series (I have also shown that the series are absolutely convergent). However, the theorem does not accomodate for dependent indices. Intuitively (using triangular summation), I think that the proper way to interchange series would be \begin{equation*} %\begin{array}{ll} \sum_{m=0}^{\infty} \sum_{n=m}^{\infty} \frac{n!}{m!(n-m)!}(b-a)^{n-m}c_n(x-b)^m = \sum_{n=0}^{\infty} \sum_{m=0}^{n}\frac{n!}{m!(n-m)!}(b-a)^{n-m}c_n(x-b)^m %\end{array} \end{equation*} and thus  $$=\sum_{n=0}^{\infty} c_n(x-a)^n$$ However, I do not know how to perform this step rigorously in case of infinite summation. Is editing sources.list a good idea? This doubt is hitting me since 2-3 days, so I decided to test it myself. What I did is I installed Ubuntu 16.04.4 in VMWare and edited /etc/apt/sources.list and replaced xenial with bionic using:  sudo sed -i 's/xenial/bionic/g' /etc/apt/sources.list   Then I ran  sudo apt-get update &amp;&amp; sudo apt-get upgrade    I was able to upgrade to 18.04, confirmed by using lsb_release -a. However, I encountered some problems like:   apt does not have a stable CLI interface. Use with caution in scripts. unmet dependency of  python3-aptdaemon.pkcompat Release 'bionic-backports' for 'appstream' not found Broken Unity   I solved all the errors and installed gnome and gdm3.   So, I just want to know is it a good idea to edit sources.list? I know that my system might broke but is there any other specific reason not to use this.  Note: I tested this on Ubuntu 16.04 in VMWare to clear my doubts only. For any triangle with sides $a$, $b$, $c$, show that $a^2b(a-b)+b^2c(b-c)+c^2a(c-a)\ge 0$ Is there a reason why people can't just take the helicopter to mount Everest? Why is it that helicopters can't reach that high? Hair particles render not same as 3dView(Eevee) Hair particle renders are not same as in 3dView(Eevee). Hair is using Principle Bsdf shader and  camera is set to Orthographic. Force and turbulence fields are applied to it. How to resolve this? How can timelapse sequences be shot without having in-camera support for it?  Which third-party tools are recommended? Why do physicists think that the electron is an elementary particle? With Glade Designer that lets you set up Gtk-Ui's you can check the option that windows are not shown in the launcher. If I take a look at the ui-file generated by Glade, it says &lt;property name="skip_taskbar_hint"&gt;True&lt;/property&gt;. In gtk code this hint is  window.set_property('skip-taskbar-hint', True). However I believe that this option is not exclusively Gtk-specific, and want to apply this one on my PyQt4-app. The Ubuntu window manager must be able to receive that hint, otherwise I would see the window of a gtk-application i use (stickynotes-indicator). So there MUST be a way of doing this in Qt or any other language, right?  Does anybody know such an option? Python or Qt syntax, doesn't matter! Proof: How many digits does a number have? $\lfloor \log_{10} n \rfloor +1$ I read recently that you can find the number of digits in a number through the formula $\lfloor \log_{10} n \rfloor +1$ What's the logic behind this rather what's the proof? Imaging new hard drive in Windows 7 laptop? I'm upgrading my Windows 7 laptop to a new hard drive.  How can I clone or image the old hard drive over to the new hard drive, so that it looks like nothing has changed (other than the new hard drive) to my operating system and applications?  Can I use what is built into Windows 7 Backup or should I use something else? Prove that $\frac{R/ \ker \phi}{(\ker \phi + J)/ \ker \phi} \cong \frac{S}{\phi(J)}$ Let $\phi: R \to S$ be a surjective homomorphism. Prove that $\frac{R/ \ker \phi}{(\ker \phi + J)/ \ker \phi} \cong \frac{S}{\phi(J)}$ for an ideal $J$ of $R.$  Obviously, $S \cong R/ \ker \phi$(first isomorphism theorem) and $\phi(J)$ is an ideal of $S$, since $\phi$ is surjective( $\forall s \in \phi(J), s = \phi(j)$ for some $j \in J, \forall s' \in S, s' = \phi(r)$ for some $r \in R$, so $ss' = \phi(j)\phi(r) = \phi(jr) \in \phi(J)$, and $ss' = \phi(r)\phi(j) = \phi(rj) \in \phi(J)$ ).  However, I'm having trouble with going on. If it's important, I mean a unitary ring by a ring. In ZFC set theory, every element object is a set. We know or feel that if $X$ and $Y$ are sets, their cartesian product $X\times Y$ is a set.  My question is: Why if $X$ and $Y$ are sets, their cartesian product $X\times Y$ is a set? DMed for the first time yesterday and one of the things I feel I need to sort out, among other comments, improvements, and similar, is how combat itself is actually initiated. The main example I want to use involves  attempting to generate surprise conditions by players. Here the characters have entered a ruined city and generally been noisy about the whole thing - using a spell to make their voice louder and literally ask if there is anyone about. Any enemies around probably know what something is about to kick off but arguably don't know precisely what. After resting the PCs head up a long flight of steps to a temple on the edge of the city. At the top only one crests and finds 3 bandits lounging around, chatting, and doing whatever bandits do in their spare time. After a brief exchange of pleasantries a combat starts:  DM &quot;The bandit spits in your direction 'we're not done looting the temple, so you can clear off', and starts raising his crossbow as his mates emerge from their cover behind the pillars... PC &quot;I cast Firebolt at Bandit Keith&quot; DM &quot;Hang on, I hadn't finished, everyone rolls for initiative...  Which sparked a debate about whether or not the PC could preemptively cast/attack before the combat starts by &quot;instant actioning&quot; (as above) as I was describing the start of the combat. As far as the bandits are concerned a lone half-elf who is pretty heavily armed has popped up in front of them, not even tried to be diplomatic, and ended up saying something rather suggestive about their mothers. The PC then asked about it being &quot;surprise&quot; because the bandits wouldn't necessarily expect an attack, but my view of &quot;surprise&quot; is closer to an ambush where one party is unaware of the other's existence. (This precise example is close to how  works, however this specific PC was always the first of the party to go into rooms (only one with darkvision) and consistently felt they should get free rounds at the start of combat based on declaring attacks before I could &quot;start&quot; the combat.) The second example the party came to more bandits, who were not alert immediately, in an underground room. They used magic to yell something obscene at the bandits and shut off all the torches so the bandits were effectively blinded. At this point they wanted to burst into the room casting spells, swinging maces, and playing some &quot;meaty chords&quot; (the bard's words, not mine). Again they wanted surprise arguing that, despite the fact that the bandits were yelling and cursing in confusion, they couldn't be sure they were actually being attacked as such. In the end a character with darkvision wanted to sneak in to a corner and again wanted surprise based on passing stealth rolls, so they would start the &quot;combat&quot; by firing a crossbow. At that point I think I relented because it was clear that they would do anything to try and win combats in a single round. In a nutshell, my question is: &quot;how liberally can the concept of surprise be applied to combat - is it only when one party is literally unaware of a threat (as I read the rules), or just when they are caught slightly off guard by the exact situation?&quot; NB I already plan to address the attempts at interrupting descriptions with actions next session, because it happened at other times and actually threw me off quite a bit.