Why do black holes warp spacetime so much more than stars that have the same mass?
When a star becomes a black hole, does its gravitational field become stronger?
What does a confidence interval with a negative endpoint mean? Find all $n\in\mathbb{N}$ so that there exist $x,y,z\in \mathbb{N}$ that solve:   $$(x+y+z)^2=nxyz$$   I tried to attack it finding solutions, but all the solutions doesn't seem to have something in common. For example:  $$ (x,y,z,n)=(1,1,1,9)$$ $$ (x,y,z,n)=(1,2,3,6)$$ $$ (x,y,z,n)=(1,4,5,5)$$ $$ (x,y,z,n)=(2,2,4,4)$$ $$ (x,y,z,n)=(8,8,16,1)$$  I was trying to solve this problem, but someone told me that a hint to solve it is using Vieta Jumping. I don't know how to use Vieta Jumping, so can anyone help me to understand how to apply Vieta Jumping and solve the problem? Careers: What does "allows remote" mean? When a posting is marked "allows remote", does it mean work in the office some days, work from home some days?  Or does it mean you could actually live out of town and maybe fly in as needed?  The reason I ask is I'm really interested in public facing software rather than internal/enterprise stuff, and most of that seems to happen in a few very expensive cities.  Given it's so hard to hire in places like SV/NYC, it seems like it could be a good scenario for companies if a developer had a really solid list of accomplishments, but I don't know how many companies think this way. I've never really thought about how the shell actually executes piped commands. I've always been told that the "stdout of one program gets piped into the stdin of another," as a way of thinking about pipes. So naturally, I thought that in the case of say, A | B, A would run first, then B gets the stdout of A, and uses the stdout of A as its input.    But I've noticed that when people search for a particular process in ps, they'd include grep -v "grep" at the end of the command to make sure that grep doesn't appear in the final output. This means that in the command ps aux | grep "bash" | grep -v "grep" it is implied that ps knew that grep was running and therefore is in the output of ps. But if ps finishes running before its output gets piped to grep, how did it know that grep was running?   flamingtoast@FTOAST-UBUNTU: ~$ ps | grep ".*" PID TTY          TIME CMD 3773 pts/0    00:00:00 bash 3784 pts/0    00:00:00 ps 3785 pts/0    00:00:00 grep How to remove Apple System Apps How can I delete Apple OS X application such as Photos, iPhoto, and others that I never use? Divergence of $\sum\limits_{n=1}^{\infty} \frac{\cos(\log(n))}{n}$ Simplify a combinatorial sum Customizing titlesec-etoc (further question) How to check that a cubic polynomial is irreducible? I want to argue that argue that $\pi(\alpha)=\alpha^3+3\alpha+3$ is an irreducible polynomial over the finite field with 5 elements $\mathbb{F}_5$. My approach was just to check that $\pi$ has no roots in $\mathbb{F}_5$. Is this right? What is the correct way to write 1.5 hours? I'm a bit confused in describing 1.5hrs in words.   Is writing one and a half an hour correct or should it be one and half hour?  E.g:     I'll see you there in one and a half an hour.     OR       I'll see you there in one and half hour.   Or is there any other correct way of writing this? I have firefox already running on my system, and now in minimised state. What I want is to close the current tab running in firefox. How can I do this by simply using commands in terminal? Promote tag wiki creation for new tags SEO scope for multiple domains hosting on the same IP address Expression Versus Statement I'm asking with regards to c#, but I assume its the same in most other languages.  Does anyone have a good definition of expressions and statements and what the differences are? How can I install the latest Netbeans? In Ubuntu Software Center the Netbeans version is netbeans 7.0.1+dfsg1-5ubuntu2 but Netbeans 8.1 is available in the Netbeans website. What should I look for when buying chain lube / lubricant? In the past, I personally have only used WD-40.   However, I have occasionally had my bicycle looked over at the locally run, free service sessions and most of the mechanics there use a hand applied type of greasy gel (I forget the name).  Questions:   Is WD-40 suitable for bicycle chains? Would alternatives provide better chain longevity? When shopping around for lubricant, what are the most important things to look for? What do you use and why?  (optional added extra) Any tips for reducing chain wear? Inspired by this ....  I am the sole person using my system with 12.04. Every time I issue a sudo command; the system asks for the user password (which is good in its own way).  However I was thinking; without activating the root account; how can I execute the sudo commands which will not ask for user password to authenticate.  NOTE: I want to execute sudo command without authenticating via password; only when they are executed via terminal. I don't want to remove this extra layer of security from other functions such a while using 'Ubuntu software center' or executing a bash script by drag-drop something.sh file to the terminal. My actual question is to find the number of transversal given a collection of set ...  After a little bit of study it has come down to:  How can we count the number of matchings in a bipartite graph with parts of size $m$ and $n$ such that it covers all $m$ vertices of the first part, $m \le n$?  I already know that there is a way to count the number of perfect matchings in a bipartite graph with $m=n$ using the permanent of its (square) incidence matrix. Possible Duplicate:          There are several tarballs (e.g. Firefox, Eclipse, Zend Studio and ...) that have executable files in them, that we can extract and run. but this executable will be available only for the user that extracts it.  If we want to make it available for all users we should move it to some location like /usr/share, /usr/local/share/, /opt/, ... and give appropriate permissions, make an executable file in /usr/bin/ and so on...  I want to make a deb installer file that does them all! How to do it? Creating all possible line segments between all points using QGIS I want to connect all points in a point feature with every possible line segment using QGIS. For example, how a pentagon has five points with ten line segments connecting them all to form a pentagram inside. Alternatively phrased: How do I make spokes when all the points are hubs? I don't care about the order, I just want every connection between two points as one line each. Is there a tool or script that can do this in QGIS? This topic () is the closest to what I want but the plugins are no longer supported.