WiFi unstable after 17.10 update
No Wifi, HP Pavillion 15 Ubuntu 14.04
How to check if file exists on FTP before FtpWebRequest Taylor's polynomial uniqueness proof - why are these limits inferable? So I'm viewing a short proof on the uniqueness of Taylor polynomials.     Uniqueness of Taylor polynomial:   Let $f:]a,b,[ \rightarrow \mathbb{R}$ $n$ times continuously   differentiable and $x_0 \in ]a,b,[$. If $p$ is $n$th degree polynomial   function for which       $$f(x)-p(x)=o(|x-x_0|^n), \space \text{when} \space x \rightarrow x_0$$  then      $$p(x)=T_{n, x_0} f(x)$$   Proof starts like:  $$\frac{p(x)-T_{n, x_0}f(x)}{(x-x_0)^n} = \frac{p(x)-f(x)}{(x-x_0)^n}+\frac{f(x)-T_{n, x_0}f(x)}{(x-x_0)^n}$$  then   $$\frac{p(x)-f(x)}{(x-x_0)^n} \rightarrow 0 \space, when \space x-x_0 \rightarrow 0$$  $$\frac{f(x)-T_{n, x_0}f(x)}{(x-x_0)^n} \rightarrow 0 \space, when \space x-x_0 \rightarrow 0$$  Now my problem is, how can one actually say that the above approach $0$ if the denominator approaches $0$? Solve the functional equation $f(xy) = f(x)f(y) - f(x + y) + 1$ and $f(1) = 2$ I'm working on this problem already, the domain and co-domain are the set of Rational Numbers. we see that setting $x = 1$ and $y = n$, we obtain $f(n + 1) = f(n) + 1$  But I'm trying to prove that $f(n) = n + 1$ for all $n$, the case when $n = 1, 2$ is obviously true, how do I approach this via induction? I've created a script that runs every night on my Linux server that uses mysqldump to back up each of my MySQL databases to .sql files and packages them together as a compressed .tar file.  The next step I want to accomplish is to send that tar file through email to a remote email server for safekeeping.  I've been able to send the raw script in the body an email by piping the backup text file to mailx like so:  $ cat mysqldbbackup.sql | mailx backup@email.com   cat echoes the backup file's text which is piped into the mailx program with the recipient's email address passed as an argument.  While this accomplishes what I need, I think it could be one step better, Is there any way, using shell scripts or otherwise, to send the compressed .tar file to an outgoing email message as an attachment?  This would beat having to deal with very long email messages which contain header data and often have word-wrapping issues etc. How can I view the camera through an object as a material in Cycles? What i did?   [root@mdfdevha1 ~]# Group_ID=`/opt/keycloak/bin/kcadm.sh get groups -r TEST`  [root@mdfdevha1 ~]# echo $Group_ID [ { "id" : "57c86153-11ba-4d19-aafb-9903ee00086b", "name" : "Admin_UserGroup", "path" : "/Admin_UserGroup", "subGroups" : [ ] } ] [root@mdfdevha1 ~]# SURE_USER_ID=`echo $Group_ID | cut -d : -f2 | awk -F\" '{print $2}'` [root@mdfdevha1 ~]# echo $SURE_USER_ID 57c86153-11ba-4d19-aafb-9903ee00086b   In this case i am able to get the id but my requirement little bit complex  I run below command   [root@mdfdevha1 ~]#  Group_ID=`/opt/keycloak/bin/kcadm.sh get groups -r My_Realm`   and then   [root@mdfdevha1 ~]# echo $Group_ID   Output was multiple record in JSON format  [ { "id" : "e27206c0-aeb6-43db-acda-c4ba43233071", "name" : "A1", "path" : "/A1", "subGroups" : [ ] },  { "id" : "89f3bd6a-33a9-4e02-9fe3-eae660c5a6cf", "name" : "Admin_UserGroup", "path" : "/Admin_UserGroup", "subGroups" : [ ] },  { "id" : "cdc2bce5-c3bb-4b88-bdaf-d87b8bb6c644", "name" : "Group104", "path" : "/Group104", "subGroups" : [ ] },  { "id" : "a0d749f2-ab6c-4c27-ad55-3357eaab9527", "name" : "Group105", "path" : "/Group105", "subGroups" : [ ] },  { "id" : "fbf99c34-d50d-408b-8d19-9713f9af3e3a", "name" : "Group106", "path" : "/Group106", "subGroups" : [ ] },  { "id" : "ebd8336f-4017-4fb1-8035-153ae1d9ba37", "name" : "Group201", "path" : "/Group201", "subGroups" : [ ] },  { "id" : "38f4aef7-caf0-4430-9e61-1ae7026e872f", "name" : "Group202", "path" : "/Group202", "subGroups" : [ ] },  { "id" : "436a0f4a-8b1b-4d7d-a014-fcec3513644e", "name" : "Group203", "path" : "/Group203", "subGroups" : [ ] },  { "id" : "41962c5f-e7e9-4748-b81f-e3f1880b78de", "name" : "Sure_Groups", "path" : "/Sure_Groups", "subGroups" : []}]   Now from the above output i want to get the ID where name = Admin_UserGroup.  How can this will achieve ? Inequality from Challenge and Thrill of Pre-college Mathematics Is there any mention of the lands east of Mordor? Sauron seems to have huge armies east of Mordor, the Blue Wizards went there and didn't come back, and early maps of Arda when it was still flat show rough landmarks, but not much, and everything changed after the Second Age.  Is there any canonical information about the East? I know $4p^4+1$ can't be square number, cause $4p^4&lt;4p^4+1&lt;4p^4+4p^2+1$ for all natural number p. But I don't know the way to prove $3p^4-3p^2+1$ can(not) be square number. Is there a well known way to prove it? Alternative for Notepad++? Stuck on two valid squares in minesweeper How to solve? The 1 indicates that ones of the two questioned flags is a mine and 3 also indicates the same. How to choose logically between any one of them? Proving that $\lim\limits_{x \to 0}\frac{e^x-1}{x} = 1$ Conceptual half-life Question So I have this word problem and I’m a bit confused about it. I have the answer and explanation but I still don’t understand: The half-life of carbon-14 is approximately 5730 years, while the half-life of carbon-12 is essentially infinite. If the ratio of carbon-14 to carbon-12 in a certain sample is 25% less than the normal ratio in nature, how old is the sample?     A. Less than 5730 years      B. Approximately 5730 years      C. Significantly greater than 5730 years, but less than 11460 years      D. Approximately 11460 years  Correct Answer: A Explanation: Because the half-life of carbon-12 is essentially infinite, a 25 percent decrease in the ratio of carbon-14 to carbon-12 means the same as a 25 percent decrease in the amount of carbon-14. If less than half of the carbon-14 has deteriorated, then less than one half-life has elapsed. Therefore, the sample is less than 5730 years old. Be careful with the wording here—the question states that the ratio is 25% less than the ratio in nature, not 25% of the ratio in nature, which would correspond to choice (D). How is the ratio of the carbon isotopes relevant to half-lives? What is the purpose of saying the half-life of an isotope is infinite? What is meant by “the normal ratio in nature”? Just based on the answer, it seems like the question said “25% of a carbon sample decayed, how old is this sample?” Obviously it’s younger than 5,730 years (the time for its first half life) because if only 25% decayed that means half a half-life has passed. I don’t see how isotopes and ratios would change this problem at all. Edit: Every answer here was very informative and helpful. It was tough to pick a best answer. I picked Cosma’s because it clicked with me. If you’re reading this and want to understand radiocarbon dating, look at every answer because there is some useful information in every answer Official reasons for "Software caused connection abort: socket write error" Which application does the vi command open? When you type vi in the terminal, the following output is shown  ~                             VIM - Vi IMproved                                 ~                                                                              ~                               version 7.3.547                                  ~                           by Bram Moolenaar et al.                             ~           Modified by pkg-vim-maintainers@lists.alioth.debian.org              ~                 Vim is open source and freely distributable                    ~                                                                                ~                        Help poor children in Uganda!                                                                                So according to this, vi must be launching VIm. But when you type  vim it gives  aditya@aditya-desktop:~$ vim The program 'vim' can be found in the following packages:  * vim  * vim-gnome  * vim-tiny  * vim-athena  * vim-gtk  * vim-nox Try: sudo apt-get install &lt;selected package&gt;   This shows that vim is not installed. Notably man vi and man vim launch the same man pages.  So what does the vi command actually launch? When should a verb be followed by a gerund instead of an infinitive? Some verbs are followed by ing, e.g. I enjoy swimming. We can't say I enjoy to swim. Likewise, some verbs are followed by to, e.g. I decided to make a plan.   Which particular verbs are followed by ing and to? Can you please provide a list for that?  Moreover, which verbs can be followed by both without having the meaning changed? power outage/frozen meat We were on vacation for a week. The neighbor said we were out of power the whole time.  We have a chest freezer full of beef. It thawed but remained in the freezer unopened the whole time. Is the meat bad if it is thawed but still cold? Can we refreeze it and eat it? How do I install .run files? To make it simple, I want to highlight a group of tikz nodes like in the following picture    It was borrowed from the . I would like to know which Tikz commands I can use to do the job in order to automatize this task for several trees I have to make. It is important to keep the blending effect of colors like in node g. Here is the MWE also borrowed from :  \documentclass{article}  \usepackage{tikz} \usetikzlibrary{arrows,backgrounds,calc,trees}  \begin{document} \thispagestyle{empty}  \begin{tikzpicture} \node (f) {f}     child { node (g) {g}       child { node (a) {a}     }       child { node (b) {b}     }   }     child { node (h) {h}       child { node (c) {c}     }   }; \end{tikzpicture}  \end{document} Determinant of a non-square matrix I wrote an answer to  question based on determinants, but subsequently deleted it because the OP is interested in non-square matrices, which effectively blocks the use of determinants and thereby undermined the entire answer. However, it can be salvaged if there exists a function $\det$ defined on all real-valued matrices (not just the square ones) having the following properties.   $\det$ is real-valued $\det$ has its usual value for square matrices $\det(AB)$ always equals $\det(A)\det(B)$ whenever the product $AB$ is defined. $\det(A) \neq 0$ iff $\det(A^\top) \neq 0$   Does such a function exist?