Why is the flight from US cities to Vietnam cheaper than from Vietnam to a US city?
Why do return flight costs vary depending on the country of origin?
How to change LCD brightness from command line (or via script)? To work around  (changing LCD brightness via hotkeys impossible), I'd like to have one command line query for increasing and one for reducing the brightness of my LCD. I could then map a hotkey to each one of this queries.  The problem is: I don't know how to increase and reduce the LCD brightness on the command line. Do you? 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? What procedure should be followed post spilling fluids onto a MacBook keyboard? I know the first thing to do is dry with a towel the majority of the fluid. Next is to turn off the computer. Then flip over the laptop itself and whilst upside down cool dry the keyboard with a hairdryer for a few minutes. Also leave the computer upside down for a day or so. Is there anything I’m missing? I've recently embarked on my PhD studies (cancer, structural biology) and have yet to publish. Currently, there are some 200 papers in my name and several thousand under my surname. Because of this, I am considering switching my surname to an old, rare, surname in my family, which is only used by one active researcher.  My question is this: are there any reasonable alternatives that does not include legally changing my name? I personally don't mind changing it, but the old surname happens to be "noble", and may come off as quite pretentious. I would be able to change to another, less pretentious, surname, but in terms of rareness, no alternative comes close.   In short, what are my alternatives? Estimating the most important features in a k-means cluster partition Is Ubuntu based on Debian unstable or Debian testing? which of the two it is? What is the formula for $\frac{1}{1\cdot 2}+\frac{1}{2\cdot 3}+\frac{1}{3\cdot 4}+\cdots +\frac{1}{n(n+1)}$ How can I find the formula for the following equation?  $$\frac{1}{1\cdot 2}+\frac{1}{2\cdot 3}+\frac{1}{3\cdot 4}+\cdots +\frac{1}{n(n+1)}$$  More importantly, how would you approach finding the formula? I have found that every time, the denominator number seems to go up by $n+2$, but that's about as far as I have been able to get:  $\frac12 + \frac16 + \frac1{12} + \frac1{20} + \frac1{30}...$ the denominator increases by $4,6,8,10,12,\ldots$ etc.  So how should I approach finding the formula? Thanks! I know that one can use "they" / "them" / "their" in place of "he" / "him" / "his" or "she" / "her" / "hers" when the subject's / direct object's gender is not known; for instance, just looking at the default user's about me section on Stack Exchange sites:     Apparently, this user prefers to keep an air of mystery about them   My question is what happens when someone wants to reference the subject using a pronoun instead.  Should the verb be conjugated accordingly to the pronoun? E.g.:     Apparently, they prefer to keep an air of mystery about them   Or should the conjugation be retained? E.g.:     Apparently, they prefers to keep an air of mystery about them   The former looks unclear because it wouldn't allow the reader / listener to understand if the writer / speaker is talking about a single person or about a group of people, however the latter sounds very weird, at least just to the non-native speaker which I am. nginx config fails with SSL key/pem (unique case) I am trying to install SSL on my nginx reverse proxy with certified ssl keys but i get this message when i try to restart server:  Restarting nginx: [emerg]: SSL_CTX_use_PrivateKey_file("/etc/nginx/conf.d/cert.key") failed (SSL: error:0906D06C:PEM routines:PEM_read_bio:no start line error:140B0009:SSL routines:SSL_CTX_use_PrivateKey_file:PEM lib) configuration file /etc/nginx/nginx.conf test failed   everyfiles are root:root with 600 permissions i've tested the certificats and they are validated with this website:   there are no trailing weird caracters in my keys, and has 64 caracter per line  here is my config file  server {     listen   443;     server_name     my.domain.com;     ssl on;     ssl_certificate      conf.d/cert.pem;     ssl_certificate_key  conf.d/cert.key;      location / {          proxy_pass         http://upstream1;          proxy_redirect     off;          proxy_buffering    off;          proxy_set_header        Host            $host;          proxy_set_header        X-Real-IP       $remote_addr;          proxy_set_header        X-Forwarded-For $proxy_add_x_forwarded_for;     }   }  Any ideas? Thank you Does a 2100W angle grinder need an earth pin? I have recently purchased a Makita 2100W angle grinder. It has just the live (L) and neutral (N) connectors unlike the one I previously used, which had a third protected earth (PE) connection.   Would it be better if I changed the connections to a 3 pin connector? How do I troubleshoot the "Error, press shutter release button again" message on my Nikon? The LCD on my Nikon D3000 is displaying the following error message:     Error. Press shutter release button again.   I have pressed the shutter release button but the camera still does not work. I want to show for $x\in\mathbb{R}$, the following inequality holds. $$ \left|\sin x\right|+\left|\sin (x+1)\right|+\left|\sin (x+2)\right|&gt;8/5. $$ This trigonometric inequality has been verified by Mathematica using the Plot commend. However, using the sum formula for the sine function seems doesn't work, and I cannot give a rigorous proof of it. Any suggestion, idea, or comment is welcome, thanks! How can I prevent SQL injection in PHP? How do I view 'git diff' output with my preferred diff tool/ viewer? When I type git diff, I want to view the output with my visual diff tool of choice (SourceGear "diffmerge" on Windows). How do I configure git to do this? I know that who is used when asking about a subject (Who is at the door?) and whom is used when asking about an object (By whom was the door opened?). How do you determine which one to use when the object becomes the subject of another clause?   For example, take the sentence:      I gave the prize to ____ deserved it most.   Would it be whomever because it's the object of "gave," or would it be whoever because it's the subject of "deserved"? Is their a hard-and-fast rule to rely on in situations like this? What's the most efficient way to get experience? Now that experience does something besides render regions of a server uninhabitable due to  orb lag, what's the most efficient and safe way to get those excellent enchants?  A mob farmer may rank highly, but what about without tons of setup? How do I make my rim brakes stop squealing? My rear rim brakes are squeaking loudly. I don't know what the problem is, but I am sure it has nothing to do with rain because it happens all the time even if it is dry.  Anybody have an idea what could be problem and how to solve it? It makes the rear brakes kind of useless, because if I use them I will scare the people or drivers around me. I never dealt with Android devices before so I'm completely newbie at it, please comment if something is too simple.  Say I purchase , that has got Android Froyo 2.2 installed in it.  If there is a new version of Android released tomorrow or next month, will I be able to update it (like I will be able to update my iPod Touch 4 to iOS 5)? Does $\int_{0}^{\infty}\frac{dx}{1+(x\sin5x)^2}$ converge? Undergraduate classical mechanics introduces both Lagrangians and Hamiltonians, while undergrad quantum mechanics seems to only use the Hamiltonian. But particle physics, and more generally quantum field theory seem to only use the Lagrangian, e.g. you hear about the Klein-Gordon Lagrangian, Dirac Lagrangian, Standard Model Lagrangian and so on. Why is there a mismatch here? Why does it seem like only Hamiltonians are used in undergraduate quantum mechanics, but only Lagrangians are used in quantum field theory?