Shouldn't string.Format be more efficcient than x + "" + y?
When is it better to use String.Format vs string concatenation?
My online friend is asking for money in order to visit my home country. Is this a legit request or a scam? Why is my total reputation less than my monthly reputation? When I went to the  to see my ranking in the reputation league, I saw this. Is this an error? My total reputation is less than my monthly reputation. Password Reset for Users on a Multisite Subsite Booting from USB and not installing I created a live usb to boot Kubuntu, which has worked well enough. However, when the installation gets to the point of telling me to restart the computer (and it restarts) the installation window pops up again, and the computer is still signed in as a live user. None of the installation or settings appear to have saved.  Any ideas? Why use the Conjure Minor Elemental spell when its results are so unpredictable? The  spell states:  You summon elementals that appear in unoccupied spaces that you can see within range. You choose one the following options for what appears:  One elemental of challenge rating 2 or lower Two elementals of challenge rating 1 or lower Four elementals of challenge rating 1/2 or lower Eight elementals of challenge rating 1/4 or lower.   It seems like the only two things a player can select are the maximum CR of the elemental conjured, and, arguably, the location its summoned in. I am confused as to why you would want to use this spell given that its results are so unpredictable. Why would a wizard cast a spell that's essentially an open invitation to whatever elemental from a list decides to show up? You can't strategize around the spell very much because, as written, you don't choose what gets summoned, and you can easily end up with something you weren't counting on. It won't be useless, but why would you cast a spell that has such an unpredictable result? It's like the difference between the chromatic orb and chaotic bolt - if the chaotic bolt didnt have the chance to bounce. You'd never pick a random damage type over a damage type of choice. Why would you choose a spell that might do something you want over something that does exactly what you intend it to do? What are the situations in which you would use this spell that wouldn't be better solved by a spell of equal or lower level that has more predictable results? How can I use asymmetric encryption, such as RSA, to encrypt an arbitrary length of plaintext? RSA is not designed to be used on long blocks of plaintext like a block cipher, but I need to use it to send a large (encrypted) message.  How can I do this? Command not found $ (dollar sign) Any command that starts with $ returns  command not found   How can I fix this?  I am  using 16.10 Ubuntu. I know that the harmonic series $$\sum_{k=1}^{\infty}\frac{1}{k}  = \frac{1}{1} + \frac{1}{2} + \frac{1}{3} + \frac{1}{4} + \frac{1}{5} + \frac{1}{6} + \cdots + \frac{1}{n} + \cdots \tag{I}$$ diverges, but what about the alternating harmonic series   $$\sum_{k=1}^{\infty}\frac{(-1)^{k+1}}{k}  = \frac{1}{1} - \frac{1}{2} + \frac{1}{3} - \frac{1}{4} + \frac{1}{5} - \frac{1}{6} + \cdots + \frac{(-1)^{n+1}}{n} + \cdots \text{?} \tag{II}$$  Does it converge?   If so, what is its sum? In the 70's or 80's I read a short story in which 2 astronauts looking for a nice place to eat lunch choose a spot at the pole of a small desolate planet, overlooking the world's only pool of surface water.  Due to the harsh extremes of heat, and lack of water, this is the home of the planet's single living organism, which has grown slowly over eons,  surviving the daily extremes, moving slowly over the bare rock, dissolving it with acidic digestive juices to get the nutrients it needs for survival. The men watch the organism while eating their lunch, then depart, unknowingly leaving death behind them in their garbage - cigarette butts, tin cans, wrappings - a bonanza that the creature moves over to dissolve and ingest, along with the human-based microscopic organisms that will destroy the alien being. The theme of the story is that although we reach out to the stars to seek life, we are much more connected to the lowest forms of life on Earth, than to any life we may find on other planets. I don't remember the author and title.  Can someone identify the story? I am travelling to Athens, Greece, shortly, and have seen . Should I be worried? Should I cancel my trip?  Update  It's fine, taxis are currently on strike, but Syntagma Sqaure is fine: Find the condition on $a$ and $b$ so that the two tangents drawn to the parabola $y^2=4ax$ from a point are normals to the parabola $x^2=4by$ Find the condition on $a$ and $b$ so that the two tangents drawn to the parabola $y^2=4ax$ from a point are normals to the parabola $x^2=4by.$  The required condition is $a^2&gt;8b^2$.I dont know how to prove it.I tried.  Let $(h,k)$ be the point from where tangents are drawn to the parabola $y^2=4ax$.Let $m_1,m_2$ be the slopes of the tangents.Equations of tangents are $y=m_1x+\frac{a}{m_1}$ and $y=m_2x+\frac{a}{m_2}$ and equations of normal to the parabola $x^2=4by$ is $y=m_1x-2bm_1-bm^3_1$ and $y=m_2x-2bm_2-bm^3_2$.  As $y=m_1x+\frac{a}{m_1}$ and $y=m_1x-2bm_1-bm^3_1$  are the same lines.Therefore,$\frac{a}{m_1}=-2bm_1-bm^3_1$  $bm^4+2bm^2+a=0$  And I am stuck.I cannot get the desired condition.Please help me. I'm working on a 2nd order passive low pass filter, consisting of two passive low pass filters chained together.         &ndash; Schematic created using   Let \$ H(s) = H_1(s)H_2(s) \$ where \$ H_1(s) \$ and \$ H_2(s) \$ are the transfer functions for each separate filter stage.  Then \$ |H(s)| = |H_1(s)||H_2(s)| \$  Knowing the magnitude of a passive low pass filter,   $$|H(s)| = \dfrac1{\sqrt{ (\omega R_1C_1)^2 + 1} } \times \dfrac1{\sqrt{ (\omega R_2C_2)^2 + 1} } = \dfrac1{\sqrt{((\omega R_1C_1)^2 + 1)((\omega R_2C_2)^2 + 1)}} $$  Then trying to find the cutoff frequency:  $$ \left(\dfrac1{\sqrt{2}}\right)^2  = \dfrac1{\sqrt{((\omega R_1C_1)^2 + 1)((\omega R_2C_2)^2 + 1)}} $$ $$ 2  = \sqrt{((\omega R_1C_1)^2 + 1)((\omega R_2C_2)^2 + 1)} $$ $$ 4  = ((\omega R_1C_1)^2 + 1)((\omega R_2C_2)^2 + 1) $$ $$ 4  = (\omega R_1C_1)^2(\omega R_2C_2)^2 + (\omega R_1C_1)^2 + (\omega R_2C_2)^2 + 1 $$  And I'm stuck. Research on the web tells me \$ \omega_c = \dfrac1{\sqrt{R_1C_1R_2C_2}} \$, but I can't find why? Can anybody show my the derivation to find this? I'm trying to make a list of ways to tell if a given degree sequence is impossible. For example $3,1,1$  is not possible because there are only 3 vertices in total so one can't have degree 3.  The list so far   vertices has degree equal to or larger than number of vertices sum of degrees is odd for n vertices if one has degree n-1 and another has degree 0 for n vertices the sum of the degrees cannot be greater than $n(n-1)$ because this would be have more edges than a complete graph Do I need an airport transit visa for Dublin, Ireland en route to the UK? I have imported a mesh (AutoCad DXF) and I'm experiencing strange shading behavior. I've done the following to try and address the problem with no luck:  Recalculate Normals Remove Doubles Delete Loose Geometry Cleared Seam, Sharp, and Bevel Weights  There are no modifiers on the mesh.  The original imported mesh looks fine in smooth shading but I need the mesh to be in quads which causes the shading to mess up as shown in photo. I can add my .blend file but I'm not sure how to do that. Why do the Localization of a Ring This question may be a bit vague, but neverthless, i would like to see an answer. Wikipedia tells me that:   In abstract algebra, localization is a systematic method of adding multiplicative inverses to a ring.   It is clear that for integral domains, we have the Field of Fractions, and we work on it. It's obvious that a Field has multiplicative inverses. Now if we consider any arbitrary ring $R$, by the definition of localization, it means that we are adding multiplicative inverses to $R$ thereby wanting $R$ to be a division ring or a field. My question, why is it so important to look at this concept of Localization. Or how would the theory look like if we never had the concept of Localization. Between you and ("me" or "I")? Is it correct to say "between you and me" or "between you and I"?  I am not a native English speaker, so please bear with me. How to backup an Android device? Can anyone recommend a good way to backup Android devices? Ideally I would like to do this wirelessly and, not only backup my data, but also my user settings. Is it possible to backup an image of an Android device - so that one doesn't even need to reinstall apps? It would be particularly useful to hear from users that have restored backups, as to how easy, and complete, their processes were. Thanks For three days straight, I have connected to the public WiFi network at my local library. Each day, I have seen a different prompt in Terminal. Here are some of the prompts I've seen:  zp-pc:~ russell$ mary-pc:~ russell$ normob05:~ russell$   I have check under System Preferences -> Sharing, and my computer name is "Russell's Mac". Also, I set the DHCP Client ID to "RUSSMAC" under System Preferences -> Network -> Advanced -> TCP/IP, but I still see the random host names at the Terminal prompt.  Why is my computer name changing every day? We are provided with a string A (may contain repeated characters as well ). One needs to make all possible permutations of A , and find out how many pairs of strings chosen from these permutations are not similar.  Two strings are similar if we can make both of them exactly same by carrying out at most 1 swap in each of them .  Example :- if we are provided with string abcd  , then for permutation abcd , the permutations which are not similar to it are bcda , bdac , cadb , cdba , dabc , dcab . Similar is the case for other permuations as well. So overall number of desired pairs are 24*6=144 .  I tried solving it for each possible pair by approach mentioned here     But as the permutations can be large enough , I need a better approach of solving this.