I have installed Ubuntu with Win 8 but at first step it blocked my Win8! Unfortunately I had to reinstall my Win8 &amp; all of my program.  I've search your site so it seems the problem is because of GRUB! So I've used these codes which I found in your site:   sudo add-apt-repository ppa:yannubuntu/boot-repair &amp;&amp; sudo apt-get update  and after that these sudo apt-get install -y boot-repair &amp;&amp; (sudo boot-repair &amp;)   and then boot &amp; repair which unfortunately I've lost my Win 8 again!!!! So I've reinstall my Win but there is no boot menu at starting my PC to choose Ubuntu or Win 8 and my PC runs with Win 8!!!  So please help me to use lovely Ubuntu with my Win 8 together without loosing anything!   Additionally I am Beginner with Ubuntu.  Thank you.
I'm absolutely new to Linux. I would like to know how to install Ubuntu alongside the pre-installed Windows 8+ OS.  Should I do it with Wubi, or through the Live USB/DVD?  What steps do I need to take to correctly install Ubuntu?
I'm runing 15.04 on a dell xps 13 bluetooth recognises devices when i  try to add them but won't let me connect to them Here is the results from my terminal.  ~ $ uname -a; lspci -nnk | grep -iA2 net; lsusb; dmesg | grep -i bluetooth; dmesg | grep -i firmware; lsmod | grep bluetooth  Linux aaron-XPS-13 3.19.0-15-generic #15-Ubuntu SMP Thu Apr 16 23:32:37 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux 02:00.0 Network controller [0280]: Broadcom Corporation BCM4352 802.11ac Wireless Network Adapter [14e4:43b1] (rev 03)     Subsystem: Dell Device [1028:0019]     Kernel driver in use: wl Bus 003 Device 002: ID 8087:8001 Intel Corp.  Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub Bus 001 Device 003: ID 0bda:5682 Realtek Semiconductor Corp.  Bus 001 Device 002: ID 0a5c:216f Broadcom Corp.  Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub [    8.164048] Bluetooth: Core ver 2.20 [    8.164065] Bluetooth: HCI device and connection manager initialized [    8.164069] Bluetooth: HCI socket layer initialized [    8.164073] Bluetooth: L2CAP socket layer initialized [    8.164079] Bluetooth: SCO socket layer initialized [    8.353160] bluetooth hci0: Direct firmware load for brcm/BCM20702A0-0a5c-216f.hcd failed with error -2 [    8.353166] Bluetooth: hci0: BCM: patch brcm/BCM20702A0-0a5c-216f.hcd not found [   20.289452] Bluetooth: BNEP (Ethernet Emulation) ver 1.3 [   20.289455] Bluetooth: BNEP filters: protocol multicast [   20.289459] Bluetooth: BNEP socket layer initialized [   20.310897] Bluetooth: RFCOMM TTY layer initialized [   20.310907] Bluetooth: RFCOMM socket layer initialized [   20.310912] Bluetooth: RFCOMM ver 1.11 [  886.399085] Bluetooth: hci0 urb ffff8800d8c15e40 failed to resubmit (2) [  895.471190] Bluetooth: hci0: BCM: patching hci_ver=06 hci_rev=1000 lmp_ver=06 lmp_subver=220e [  896.113983] Bluetooth: hci0: BCM: firmware hci_ver=06 hci_rev=1624 lmp_ver=06 lmp_subver=220e [    8.353160] bluetooth hci0: Direct firmware load for brcm/BCM20702A0-0a5c-216f.hcd failed with error -2 [  896.113983] Bluetooth: hci0: BCM: firmware hci_ver=06 hci_rev=1624 lmp_ver=06 lmp_subver=220e bluetooth             491520  22 bnep,btusb,rfcomm ~ $ Remove all content using pure JS Why do the major and minor groove exist in DNA? So I know that the major/minor groove arise from the offset pairing of the two strands in the helix.  All my textbook tells me is that "pitch causes the off-set pairing of DNA and this gives rise to the major and minor grooves."  I'm not too sure what this is saying.  What exactly is pitch and how does it give rise to the grooves? I know this question is someway similar to  where they recommend using 404, but after reading  where they suggest to use 301 when changing site URLs (in the specific case was due to redesign/re factoring) I get a bit of confused and I hope someone could clarify for this specific example:   Let's say I have an eCommerce site, let's also say the final user inserted some interesting items in the site and the eCommerce webapp created the item pages at the URLs: http://...?id=20, http://...?id=30 etc. Now let's say some of these interesting items got many external links toward them from many other sites because some people found those items very interesting and linked to them. After some years the final user deletes those items, so obviously the pages and URLs http://...?id=20, http://...?id=30, etc. now do not exist anymore, but still many pages on the web are linking toward them.   What should the eCommerce site do now, just show a 404 page for those items?  But, I'm confused, wouldn't this lose all the Google PR passed by the external links to the items pages? So isn't it better to use 301 redirect to HOME PAGE that at least passes the PR to the HOME PAGE?    EDIT:  Well, according to answers the best thing to do so far is to do a 404/410.  In order to make this question more complete, I would like to talk about a special case, just to make sure I understood. properly.  Let's say the user creates those items again (the ones he previously deleted at point 4), maybe he changes a bit their names and description, but they are basically the same items. The webapp has no way to know these new added items were the old items so it obviously create them as new items with new URLs http://...?id=100, http://...?id=101, does it makes sense at this point to redirect 301 the old urls to the new ones?    ANOTHER EDIT (It would be VERY IMPORTANT TO UNDERSTAND):  Well according to the clever answers received so far it seems for the special case, explained in my last EDIT, I could use 301, since it's something of not deceptive cause basically the new pages is a replacement for the old page in term of contents. This is basically done to keep the PR passed from external link and also for better user experience.  But beside the user experience, that is debatable (*1), in order to preserve PR from external broken links why not just always use 301, In my understanding Google dislikes duplicated contents, but are we sure that 301 redirect to HOME PAGE is seen as duplicated contents for Google?!   Google itself  so if they consider 301 as duplicated contents wouldn't that be considered duplicated contents too? Why do they suggest it?  Let me provoke you: “why not just add a 301 to HOME PAGE for every not found page?”   (*1) as a user, when I follow a broken URL from some external link to some website's page I would stick more on this website if I get redirected to HOME PAGE rather than seeing a 404 page where I would think the website does not even exist anymore and maybe I don't even try to go to HOME PAGE of the website. Universal extractors With an  of archive/compression file formats, is there a single free/open-source command line tool to rule them all? Perhaps something with a consistent / unified set of flags? (note my  friendly )  I once run into a set of aliases meant to largely simplify the task of compressing/de-compressing files with bindings to tar and other utils, but I can't find this anymore.  Update: How can I configure something like atool to not use unzip to extract zip files (which apparently can't handle files larger than 4GB) and to use gunzip instead?  $ aunpack large_file.zip error:  Zip file too big (greater than 4294959102 bytes) Archive:  large_file.zip warning [large_file.zip]:  1491344848 extra bytes at beginning or within zipfile   (attempting to process anyway) error [large_file.zip]:  start of central directory not found;   zipfile corrupt.   (please check that you have transferred or created the zipfile in the   appropriate BINARY mode and that you have compiled UnZip properly) aunpack: unzip ...: non-zero return-code Being characteristic is transitive Here, I wanted to verify that:     The property of being characteristic is a transitive relation among subgroups of a group $G$.   For subgroups $N,H\leq G$, we have $N$ char $G$ and $H$ char $N$. So $N$ char $G$ implies: $$\forall\psi\in Aut(G); \psi(N)=N$$ $H$ char $N$, so for all elements in $Aut(N)$, $H$ is remained never changing. Especially, when I take $\psi'=\psi|_{N}$ then $\psi':N\to Aut(N)$ would be in $Aut(N)$ and $\psi'(H)=H$. Since the last equality is true for $H$ and the maps, caused by restriction on $N$, then I have $H$ char $G$.  Honestly, I am inly not satisfied form the conclusion here and think I am losing something. Thanks for your hints. How to make sure one understands each and every detail while reading a textbook/research paper without leaving any gaps? I am a physics Master's student.  I have good grades, with CGPA above 9(/10)(However, all courses in my university are graded on a curve so the actual marks are significantly lower than 90%). This has been my marks throughout my undergraduate and graduate courses and I was happy because this was above average. Also, my summer projects in UG were usually computational and any difficulty I had in theoretical aspects I attributed it to my inexperience in advanced Physics.   However, recently I have started to work on pure theoretical project and while reading for the project I realized that I consistently miss some details from each topic. I understand the general idea, can re-derive most of the equations(with some effort) however when I discuss things with my professor or when I read further topics I realize that I have missed certain key-details. This is exactly similar to the case of me missing a few key questions in my exams and getting that 9 grade point instead of 10(or at-least I think so). I was not worried about this before but now I realize that there is some flaw in the way I study (but I do not know what).   Since I want to apply for Physics PhD I realized that I will need to have solid concepts and it would be best to correct my mistakes but I do not know how or even what could be the reason for my imperfect understanding.  Any direct suggestion would help or even certain general guidelines on what I can do.    Things I've tried recently -   1) I've started to written down almost everything I read. This is slightly laborious but is certainly helping. It also helps me to gloss over the things I read previously when I come back the next day.  2) I completely avoid smartphone when I'm library/study room so that I won't get distracted. Not sure if it helps me solve the above problem but certainly helps me study better in general.  3) I've tried to read the topics from several sources. The books I am reading is somewhat like a collection of research papers and hence does not have a exercises. So I though reading from various sources might help get better ideas but it's not really helping because most other sources are too high level as an introductory text. But this will probably help me in cases where it's practical to do this.  4) Somewhat similar to point (1)- I am trying reread, whenever I can, what I've done until that point. But not sure how much this will help me in filling the gaps. Pressing "W" turned my cursor into a circle What is the structure in "as best you can"? I instinctively translate it "as best as you can", however this makes no sense.  What is the real structure behind this phrase?  I'll include an  to illustrate the historical presence of this phrase:    Whatever the structure is, I'm guessing that it has something to do with 19th century grammar. Schengen Visa Refusal: Justification for the purpose and conditions of the intended stay was not reliable Schengen refusal formulae can be difficult to understand sometimes.  Sometimes an applicant receives a refusal with:       Justification for the purpose and conditions of the intended stay was not reliable.     often accompanied by:       Your intention to leave the territory of the Member States before the expiry of the visa applied for could not be ascertained.   What is meant by this refusal reason?  What are they trying to say? Decrease available inventory item on Cognito Form, removing it when zero I want to limit inventory quantities on a sales form, so that it can start at say 100 and count backwards as applicants submit orders and then shut down that particular option when it reaches 0.    Is this possible with Cognito? In an Integral Domain is it true that $\gcd(ac,ab) = a\gcd(c,b)$? In my algebra class I was given as homework assignment to prove that:     Given an integral domain $A$ and $a,b,c,d,e \in A$. Then if $d = \gcd(b,c)$ and $e = \gcd(ac, ab)$ then $e = ad$.   It is easy to see that $ad \mid ab$ and $ad \mid ac$, so this implies that $\exists q \in A; e = q(ad)$. Now I'm having problems showing that $q = 1_A$. Working through some equalities, I proved that $\forall n\in \mathbb{N}, q^n \mid d$ so this gives me the light suspicion that I might be going the right way, but I'm pretty positive that this does not imply $q = 1_A$.  Does anyone want to give me a hint?  Thanks in advance :) How to permanently allow location access for a website in Safari 11? Sharing a Bluetooth Keyboard and Mouse sequentially between two Macs How to answer a negative question in English? Q: "Don't you know?"   If I really don't know, how should I respond to this question? Yes or No?  There's a similar question on EL&amp;U, but the answer isn't clear how it works:      Also here on ELU too:      These answers are confusing. I want to know what one word answer I can use. In other words I want to know:   What will native speakers understand if I reply No to this question? What will native speakers understand if I reply Yes to this question? What is so bad about singletons? Wirtinger Inequality: $\int_0^1 f'^2 \geq \pi^2 \int_0^1 f^2 $ I have a  basic question  Let $f$ be a $\mathcal{C}^1$  map  from  $[0,1]$ into $\mathbb{R}$ vanishing in $0$ and $1$. I want to prove that   $$\int_0^1 f'^2 \geq \pi^2 \int_0^1 f^2 $$  and to see when we have equality. Error handling in C code What do you consider "best practice" when it comes to error handling errors in a consistent way in a C library.  There are two ways I've been thinking of:  Always return error code. A typical function would look like this:  MYAPI_ERROR getObjectSize(MYAPIHandle h, int* returnedSize);   The always provide an error pointer approach:  int getObjectSize(MYAPIHandle h, MYAPI_ERROR* returnedError);   When using the first approach it's possible to write code like this where the error handling check is directly placed on the function call:  int size; if(getObjectSize(h, &amp;size) != MYAPI_SUCCESS) {   // Error handling }   Which looks better than the error handling code here.   MYAPIError error; int size; size = getObjectSize(h, &amp;error); if(error != MYAPI_SUCCESS) {     // Error handling }   However, I think using the return value for returning data makes the code more readable, It's obvious that something was written to the size variable in the second example.  Do you have any ideas on why I should prefer any of those approaches or perhaps mix them or use something else? I'm not a fan of global error states since it tends to make multi threaded use of the library way more painful.  EDIT: C++ specific ideas on this would also be interesting to hear about as long as they are not involving exceptions since it's not an option for me at the moment... PHPExcel Sumif and Skip Show that if $g \circ f$ is injective, then so is $f$. The Problem:  Let $X, Y, Z$ be sets and $f: X \to Y, g:Y \to Z$ be functions.  (a) Show that if $g \circ f$ is injective, then so is $f$.  (b) If $g \circ f$ is surjective, must $g$ be surjective?  Where I Am:  So, I really have trouble with these, for some reason. I can draw pictures and make sense of the problems, but writing down proofs is very difficult for me.   Basically, for (a), I ended up with some complicated statement involving an implication implying another implication and then tried to derive a contradiction. It just got so convoluted that I couldn't make sense of it anymore, and I know there's a quick, elegant way to show it.  For (b), I know that $g$ need not be surjective. Once again, though, proving it directly from definitions has given me a bit of a headache.  Any help here would be appreciated. Thanks in advance.  The Proofs!  Ok, I did it. Thanks for the help, everyone! Let me know if there's anything wrong with these proofs, or if they could bet any better.  (a) Suppose $f$ is not injective. Then $$ f(x_1)=f(x_2) \implies x_1 \ne x_2 \text{        }(*).$$ Let $f(x_1)=y_0=f(x_2)$ and let $g(y_0)=z_0$. Then $$ (g \circ f)(x_1) = (g \circ f)(x_2) = g(y_0) = z_0. $$ Since $g \circ f$ is injective, $$ (g \circ f)(x_1) = (g \circ f_2) \implies x_1 = x_2. $$ However, this contradicts $(*)$. Therefore, $f$ must be injective.  (b) Suppose $g$ is not surjective. Then  $$ \forall y \in Y, \exists z \in Z \text{ such that } g(y) \ne z \text{         }(**).$$  Since, $g \circ f$ is surjective,  $$ \forall z \in Z, \exists x \in X \text{ such that } g(f(x)) = z \text{       } (***). $$  Let $f(x) = y$. Then,  $$ g(f(x)) = g(y) = z. $$  Because of $(***)$, this is true for all $z \in Z$, which contradicts $(**)$. Therefore, $g$ must be surjective.