I'm looking into buying a lufthansa economic flex ticket so if something happens and I am forced to cancel my trip under any circumstance, then I can get my money back (I'd cancel the entire trip, outbound and inbound). My question is if I can just cancel my ticket and get my money back ? (I assume I'd have to pay some fee).
Lufthansa airline offers the &quot;Economy Flex&quot; fare. The listed advantages of this fare are:  Rebooking possible plus fare difference Refundable except 70 EUR plus fare difference  What does the &quot;plus fare difference&quot; mean? Imagine I buy a ticket for 200 €. Later I decide to cancel. They keep 70 Euro, so I get 130€ back. What's with the fare difference? Fare difference to what? As a comparison, the &quot;Economy classic&quot; states:  Rebooking: 70 EUR plus fare difference Refund not possible
That is,     why is $\varphi(AB)=\varphi(A)\varphi(B)$, if $A$ and $B$ are two coprime positive integers?   It's not just a technical trouble—I can't see why this should be, intuitively: I bellyfeel that its multiplicativity should be an approximation at most. And why the minimum value for $\varphi (n)$ should be $ \frac{4n}{15} $ completely passes me by. Jenkins + git: "tell me who you are" error, why does it need to tag? Outlier Detection on skewed Distributions Under a classical definition of an outlier as a data point outide the 1.5* IQR from the upper or lower quartile, there is an assumption of a non-skewed distribution. For skewed distributions (Exponential, Poisson, Geometric, etc) is the best way to detect an outlier by analyzing a transform of the original function?  For example, distributions loosely governed by an exponential distribution, could be transformed with a log function - at which point is it acceptable to look for outliers based on the same IQR definition? I see ads to other SE sites regularly on the sidebar of SO. Are these questions chosen by hand, or algorithmically? The reason I ask is that there was an ad pointing to  on Seasoned Advice. I'm all for a good laugh I suppose, but is this the kind of question that should be highlighted?  It's obviously a thriving community, but if this were my first exposure to that community, and I saw that the highest-rated answer -- from the user with the highest reputation -- was (and I paraphrase only lightly):  &quot;Why yes, there is tool that can cut cherry tomatoes in half.  It's fantastic for the job.  It's called a freakin' KNIFE!&quot;  would I ever want to visit again, let alone ask a question over there? First impressions count for a lot, and that one missed the mark IMHO. If the selection method is algorithmic, I suppose there's no reliable way to detect sarcasm in a highly-rated answer, but if it's manual, weeeellllllllll ... :) "Hot" tab in is badly skewed and misleading - time to replace it with actual hot questions? Each site got a &quot;hot&quot; tab, where its contents are calculated based on . However take a look on the screenshots below and see for yourself that &quot;hot&quot; got nothing to do with many of the questions listed there. :    :    As you can see, there are questions with negative score, no answers, and even closed. I won't be surprised to see spam in there as well. This can't be any worse. What I suggest, instead of fixing the formula or patching it, simply have the hot tab show the same questions as the Hot Network Questions sidebar. (from the specific site only, of course.) Since the hot questions &quot;pool&quot; (as seen ) is limited to 100 for the whole network, either expand it or have the per-site list show questions with less hotness points - it would still be better than what we have now. Proving by induction that $\sum\limits_{k=2}^n \frac1{k^2}\le 1$ I mean, why is $F=ma$? Why not $m^{0.123}$, $a^{1.43}$ or some random non-integers or irrational?  I hope you understand that my question isn't limited just to force, energy, velocity, etc.; it also extends to the area of a square, circle, etc. and all other formulas.  I think the whole thing starts with direct proportionality.  Most of them tell about the area of a circle, $A = πr^2$, where π is 3.14159..... an irrational number! It's not about the constant. I am talking about the power of a physical quantity.  I know why it has pi. It's because we chose the constant for area square to be one. If we chose it to be 1 for the circle then the area of a square will have a constant, 1/pi.   I've edited the question to 'rational exponents' since all are giving me examples of decimal non-integers. Landau's derivation of a free particle's kinetic energy- expansion of a function? I was reading a bit of Landau and Lifshitz's Mechanics the other day and ran into the following part, where the authors are about to derive the kinetic energy of a free particle. They use the fact that the Lagrangian of this particle must be the same (or at most, differ by the total time derivative of a function of co-ordinates and time) in different inertial frames.     We have $L'=L(v'^2)=L(v^2+2\mathbf{v}\cdot\boldsymbol{\epsilon}+\boldsymbol{\epsilon}^2)$. Expanding this expression in powers of $\boldsymbol{\epsilon}$ and neglecting terms above the first order, we obtain    $$L(v'^2)=L(v^2)+\frac{\partial L(v^2)}{\partial (v^2)}2\mathbf{v}\cdot\boldsymbol{\epsilon}.$$   I think I'm ok with all the physics in this section. What I don't get is just the part I quoted above (so maybe this post is better suited for the math site, but since this is book is so physics-y I thought I'd post it here). My math is pretty rusty, so I'm not really sure- how do the authors expand the function to arrive at the above expression? It reminds me a bit of a Taylor expansion, but not very much. What's the process used to arrive at it? Is it possible to upgrade the graphics card in modern laptops? As there's no definitive answer to this, and I would prefer not to be too specific about particular models, what are the things that determine whether this is possible or not?   What expansion slots would the laptop require to do this? How can you find out if a motherboard/chipset supports upgrades?  Is heat an issue? Could it void the warranty? How is battery life affected? On my Amazing 2GB EeePC Surf, I have no more space left!  This is quite normal, and it happens every now and then. Just delete a few large, unneeded files and everything should be good, right?  So I go and find a 2MB file in /tmp, and rm -rf it. Check free space again, and -- still nothing?!  I had to remove about 30MB of files before it registered some free space.  Now, my question is, what's up with this strange behaviour? My Applications are not showing after upgrading from Ubuntu 18.04 to 20.04 I did an upgrade today to the latest version of ubuntu. Everything looked good and fine only for me to discover that I cannot find my applications after clicking the 'Show Applications' icon. The same applies when I search for an application in the search bar, I do not see it. It shows me an endless search.  These are the screenshot images of the problem:      In the meantime, I access my applications from the menu at the top bar and also use the terminal to run applications with CLI. One of my favorite quotes is by Alvin Toffler which says:     The illiterate of the 21st century will not be those who cannot read   and write, but those who cannot learn, unlearn, and relearn.   The way I understand "relearn" in the quote is to learn something new that is different from what was originally learned.  I'm wondering in general if "relearn" convey learning the same thing again, or a different thing, or it depends on the context of the sentence. Is the same thing true for "learn again"? Let's say we have a cloud of dust which is a lightyear across and someone shoots a beam of light from point A to B , why it is not possible for an observer far far away to see the light while it travels through the cloud at the speed of light? Lock in mysql database "std::endl" vs "\n" Many C++ books contain example code like this...  std::cout &lt;&lt; "Test line" &lt;&lt; std::endl;   ...so I've always done that too. But I've seen a lot of code from working developers like this instead:  std::cout &lt;&lt; "Test line\n";   Is there a technical reason to prefer one over the other, or is it just a matter of coding style? How to get Intel Dual Band Wireless-AC 3168 work on Ubuntu 16.04? How do I  prevent .xsession-errors from eating disk space? Is there any way to completely disable the .xsession-errors file?  I have it as a symlink to /tmp so that my laptop hard disk can (hopefully) go to sleep for once, but at least 95% of the stuff in the file (it fills up at about 500k an hour) is...  (nautilus:1618): GLib-GObject-CRITICAL **: g_value_get_object: assertion `G_VALUE_HOLDS_OBJECT (value)' failed  which is total garbage to me.  I have tried doing a symlink to /dev/null but that does not work (the resulting link is overwritten), and I also do not want the activity so that hopefully my laptop can go to sleep for once.  I am using Ubuntu 11.04, with no special add-ons to Nautilus. How to run two Thread Group in a loop - JMeter I'm facing problem here, There are 2 Thread Groups  and both are correlated ( run thread group consecutively is ticked in test plan ).  1st is user thread group and 2nd is Driver thread group. So thread group running concurrently but it is not happening in twice. I've put loop count for 2 they will run each independently after completion of first cycle. I want run this flow such a way that after completion of driver group request next do second iteration (start from user) thread group. So how to do this stuff ?  Loop will be :   User thread group Driver Thread group   After completing this once again start with :   User thread group Driver thread group   like this it should(loop) happen for multiple times How do I turn off the Minecraft 1.7.2 Super Secret Settings? How do I turn off the Minecraft 1.7.2 super secret settings? I tried F3 and F4, hitting Esc repeatedly, all things mentioned on blogs – nothing is working. How can I export the "available software to download" to a file? Sometimes Ubuntu will show a popup like this:    (It looks weird because I'm using )  How can I export the list of packages/changes Ubuntu wants to install to a file? This is for debugging purposes - I think something in this update is breaking my system, and I want to be able to be able to figure out exactly where the break is coming from.