I want to download and use Ubuntu
Where can I get an Ubuntu Installation CD/DVD/USB?
This is a question in Ahlfors in the section on the argument principle: How many roots of the equation $f(z)=z^4+8z^3+3z^2+8z+3=0$ lie in the right half plane?  He gives a hint that we should "sketch the image of the imaginary axis and apply the argument principle to a large half disk."  Since $f$ is an entire function, I think I understand that the argument principle tells us that for any closed curve $\gamma$ in $\mathbb{C}$, the winding number of $f(\gamma)$ around 0 is equal to the number of zeros of $f$ contained inside $\gamma$.  How would you go about actually applying the hint though? I am having trouble figuring out what the image of a large half disk under $f$ would look like. Open Finder window from current Terminal location? If I am in a specific path in a Terminal window, how can I open that same window in a new Finder window?   Note: This is the opposite of . sudo on Windows 10 Linux subsystem cannot resolve local machine name I installed Windows 10 Anniversary update and the Linux subsystem. When running anything with sudo it takes ages and then I get this error message:     sudo: unable to resolve host MYMACHINE   How to get rid of this and make sudo fast? Can Blender render pngs with the background transparent? I would like to render an animation as a series of .png images with transparent backgrounds for use in a video. Is this possible? I'll be arriving at Heathrow in June 2015 with my current girlfriend for a holiday in the UK. I've been trying to find out which immigration queue to join at Heathrow Passport Control without much luck. I have a British passport, my girlfriend has a non-EU passport.     Should I join the EU queue and she the non-EU queue or should we both queue together (and if so, which of the queues should we join)? On the websites, whenever the OP comments on an answer, or on his question, his name is highlighted. This is a handy feature because you can easily tell whether the comment is from the OP or not.   But on the Android mobile app (don't know about iOS),  this feature is not there. Can we have it please!? Patching commands to remove surrounding whitespace I'm using the todonotes package to add little margin notes to my text, however writing  Hello\todo{test} World!   removes the interword space as is already pointed out in . So I tried  \pretocmd{\todo}{\@bsphack}{}{} \apptocmd{\todo}{\@esphack}{}{}   and this adds the interword space but simply outputs all parameters instead of passing them to \todo.  Full MWE:  \documentclass{article}  \usepackage{etoolbox} \usepackage{todonotes}  \makeatletter \pretocmd{\todo}{\@bsphack}{}{} \apptocmd{\todo}{\@esphack}{}{} \makeatother  \begin{document} Hello\todo{test} World! \end{document} Problem in solving functional equation $f(x^2 + yf(x)) = xf(x+y)$ To find all functions $f$ which is a real function from $\Bbb R \to \Bbb R$ satisfying the relation  $$f(x^2 + yf(x)) = xf(x+y)$$  It can be easily seen that the identity function $i.e.$ $f(x)=x$ and $f(x)=0$ (verified just now) satisfies the above relation!! And putting $y=0$ I have got $f(x^2)=xf(x)$.  Help needed to find other functions satisfying the relation. Windows Unable to Delete ._. File How can I make Firefox open magnet-links in Transmission? What are the fundamentals of implementing hook_menu()?  I would like to see the basics covered in a single question, to avoid having to answer the same similar but different questions over and over. Textbook recommendation for computational physics How to align text in TikZ nodes by baseline? I need to draw a graph where some nodes have the same y-coordinate. I want the text within the nodes on the same y-coordinate to be baseline-aligned. However, the text seems to be aligned by the bottom lines, not the baseline.   Here's what I tried to do:  \documentclass[final,t]{beamer} \mode&lt;presentation&gt; \usepackage{tikz} \usepackage{pgfplots} \tikzstyle{gate2} = [circle,fill=white,draw=black,minimum size=1cm] \begin{document}     \begin{tikzpicture}         \node[gate2] (mu_0) at (0, 0) {$\mu_0$};         \node[gate2, baseline = (mu_0.base)] (Lambda_0) at (2,  0) {$\Lambda_0  $};     \end{tikzpicture} \end{document}   What I see is that the shapes are at the same y-coordinate (as expected), but mu is higher than Lambda. How do I specify that mu and Lambda should be on the baseline? I've been trying to prove   $$\sum_{k=1}^{n}{(-1)^{k+1} {{n}\choose{k}}\frac{1}{k}=H_n}$$  I've tried perturbation and inversion but still nothing. I've even tried expanding the sum to try and find some pattern that could relate this to the harmonic series but this just seems surreal. I can't find any logical reasoning behind this identity. I don't understand . Is there any proof that doesn't require the integral transform? I need scale up video from one DOS game using . But with  on left side and  filter on the other one.  Input (320x200)    Output (1280x800)    Here is a command, where's xBR processing whole screen...  ffmpeg     -i input.avi     -sws_flags neighbor     -vcodec libx264 -strict -2     -preset veryslow -qp 0     -filter:v "xbr=4"     output.mp4 I recently got a new router, a DRL-600L Router from D-Link, and was setting up some filters to block out certain websites.  One problem I am having is blocking out addresses that use https instead of http.  For example, I'm trying to block out Facebook, because Facebook.   So far, the filter filters http://www.facebook.com perfectly fine, but for the url https://www.facebook.com, it won't block that.  How can I block those kinds of websites? How to switch from Natbib to Biblatex in pre-made document class/template? I am using  to write my thesis. The template uses Natlib for references, whereas I really need Biblatex.   When I simply try to change \usepackage[natbib] for biblatex I get the error message  This is BibTeX, Version 0.99d (TeX Live 2016/Debian) Capacity: max_strings=100000, hash_size=100000, hash_prime=85009 The top-level auxiliary file: aagot-1-report.aux The style file: acm.bst Illegal, another \bibstyle command---line 80 of file aagot-1-report.aux  : \bibstyle  :          {acm}  I'm skipping whatever remains of this command Database file #1: Mendeleytry.bib.bib Warning--I didn't find a database entry for "" You've used 14 entries,code here   The solution  \usepackage[backend=bibtex, natbib=true, style=numeric]{biblatex}   didn't work.  Another possible solution was said to be to recompile from scratch to delete the .aux file, but that resulted in  /usr/share/texlive/texmf-dist/tex/latex/biblatex/biblatex.sty:462: LaTeX Error:  Command \bibhang already defined.            Or name \end... illegal, see p.192 of the manual.  See the LaTeX manual or LaTeX Companion for explanation. Type  H &lt;return&gt;  for immediate help.  ...                                                l.462 \newlength{\bibhang}   I have tried to use this "marco" to override the \requirePackage settings, but that also didn't work and resulted into  LaTeX Error: Two \documentclass or \documentstyle comm ands.  See the LaTeX manual or LaTeX Companion for explanation. Type  H &lt;return&gt;  for immediate help.  ...                                                l.45 \documentclass[whitelogo]{                            tudelft-report}    Where I can't seem to delete any of the document classes without getting the functionality of the tudelft-package and the biblatex citing (or in fact getting it to work at all!)  (no line number): [0] Config.pm:343&gt; INFO - This is Biber 2.5 [0] Config.pm:346&gt; INFO - Logfile is 'aagot-1-report.blg' [62] biber:290&gt; INFO - === Tue Apr 24, 2018, 22:24:06 [246] Utils.pm:165&gt; ERROR - aagot-1-report.bcf is malformed, last biblatex  run probably failed. Deleted aagot-1-report.bbl [246] Biber.pm:113&gt; INFO - ERRORS: 1   Is there any way I can still make this template work with Biblatex? Natlib seems to deeply rooted in the file and I don't know how to change it/access the settings/the ".sty"-file. Can I use the example documentclass combined with biblatex (instead of the standard natbib) without losing the great parts of the rest of the document class?  Thanks very much :) Options for object creation are greyed out I am trying to model a tree. I turned on the Add a sapling add-on in user preferences, however once I want to begin editing the settings, they come up but is grey and doesn't let me click on it.    I have also attached my blend file here: Why do some websites show the company name next to the URL? Some websites show the company name next to the URL (in Chrome) and some don't.  How do I set this up for my website? Is there a reason why or why I wouldn't want to do this? Today I was thinking about composition of functions.  It has nice properties, its always associative, there is an identity, and if we restrict to bijective functions then we have an inverse.  But then I thought about commutativity.  My first intuition was that bijective self maps of a space should commute but then I saw some counter-examples. The symmetric group is only abelian if $n \le 2$ so clearly there need to be more restrictions on functions than bijectivity for them to commute.  The only examples I could think of were boring things like multiplying by a constant or maximal tori of groups like $O(n)$ (maybe less boring).  My question: In a euclidean space, what are (edit) some nice characterizations of sets of functions that commute? What about in a more general space?   Bonus: Is this notion of commutativity important anywhere in analysis?