how to install NS2 on linux correctly. because many tutorials cannot be run. ask for help please yes because I'm still a beginner in using Linux Ubuntu. thank you.
If I upgrade Ubuntu 12.04 to 14.04, will NS2 still be supported?  I am currently using NS2 on Ubuntu 12.04.
Finding the sum of series $\sum_{n=0}^∞ \frac{2^n + 3^n}{6^n}$ Does there exist an $a_0$ such that the sequence $a_{n+1} = 2a_n + 1$ is prime for all $n \ge 0$? I believe I see that $a_n = 2^n(a_0+1) - 1$ but am somewhat uncertain where to proceed afterwards. I am a complete beginner at number theory and would appreciate it if someone could point me in the right direction--surely there is some obvious argument I am missing. Is it possible for test error to be lower than training error Is it possible to have test error lower than training error?  I have a classification problem with 2000 samples, 500 of which are positives, 1500 are negatives. I split my data into 70% training data, 30% test data.  Run random forest with 200 estimators and cv=10. I did this several times and compared the recall and precision score and notice the scores for my test set is significantly better. Is this possible? Im new to Illustrator and have found the clipping mask is not so easy compared to Phtoshop. Could any one tell me how i can make this line texture a clipping mask over the circle? Is static HTML the fastest? I have been researching several different techniques to deliver web content fast, like nginx and node.js.  When it comes down to performance optimization http expires headers and gzip come to mind. After that come common techniques like sprites and CDNs etc.  But I am wondering.  What would be the very fastest technique to load a website?  Is static html the very fastest that can be? Or is there something else even faster? In many machine learning applications, the so called data augmentation methods have allowed building better models. For example, assume a training set of $100$ images of cats and dogs. By rotating, mirroring, adjusting contrast, etc. it is possible to generate additional images from the original ones.  In the case of images, the data augmentation is relatively straightforward. However, suppose (for example) that one has a training set of $100$ samples and few hundred continuous variables that represent different things. The data augmentation does not anymore seem so intuitive. What could be done in such case? Unresponsive KeyListener for JFrame Wifi problems with rtl8723be in Ubuntu 14.04 How do I run a sudo command in Emacs? postfix - how to prevent users from sending with another users name Even though my postfix server cannot be used without authentification (open relay), sending mail in another users name after logging in is still possible like this:  EHLO domain.org auth plain eW91IGxpdHRsZSBkaXJ0eSBiYXN0YXJkIDstKQ== 235 2.7.0 Authentication successful mail from: otheruser@domain.org 250 2.1.0 Ok rcpt to: recipient@otherdomain.org 250 2.1.5 Ok data 354 End data with &lt;CR&gt;&lt;LF&gt;.&lt;CR&gt;&lt;LF&gt; Please send me your account info. . 250 2.0.0 Ok: queued as D40692A61AA quit   How can this be prevented? Trouble with batch conversion of .png to .pdf using convert Tangent and Normal lines that pass through the origin Let $\alpha$ be a regular curve in $\mathbb{R}^2$ and let all of its tangent lines pass through the origin. Also, let $\beta$ be a regular curve in $\mathbb{R}^2$ and let all of its normal lines pass through the origin.   How can I show that $\alpha$ is contained in a straight line through the origin and that $\beta$ is contained in a circle around the origin?  I know that the tangent line $\alpha(t)$ is the line that points in the direction of the tangent vector $T(t)$ and that the normal line of $\beta(t)$ is the line that points in the direction of $N(t)$, but how can I put this all together to complete the proof? Doubt regarding a limit which is related to MVT Let the function $f(x)$ be differentiable  and $f'(x)$ be continuous in $\left(-\infty,\infty \right)$ with $f'(2)=14$ then evaluate the limit  $$\lim_{x\to 0}\frac{f(2+\sin x)-f(2+x\cos x)}{x-\sin x}$$  My attempt:  $\lim_{x\to 0}\frac{f(2+\sin x)-f(2+x\cos x)}{x-\sin x}$  $\lim_{x\to 0}\left(\frac{f(2+\sin x)-f(2+x\cos x)}{\sin x-x\cos x}\right)$ $\frac{\sin x-x\cos x}{x-\sin x}$$=\left(f'(2)\right)(2)=28$  Is the method used here correct What are the advantages and disadvantages of using ARC? I need to find all group homomorphisms of $S_n\to\mathbb{C}^*$ (for $n\ge2$), and also all group homomorphisms of $A_n\to\mathbb{C}^*$ (for $n\ge2$).  Someone on this site, two years ago, seems to have already asked the same question (). I understand what the questioner says there, but I don't understand it when he says:     Therefore there is exactly one $g:\mathbb{Z}/2\mathbb{Z}\to\mathbb{C}^*$, so all elements of $a\in\mathbb{C}^*$ give us $\operatorname{ord}(a)\mid g[\mathbb{Z}/2\mathbb{Z}]$, so $a$ can only be $-1$ or $1$. Now we know that $f:S_n\to\{-1,1\}$ &hellip;   What is he saying there? And how to go on from there? (I do not understand the answer given either &hellip;)  I hope that someone here can help me further. (And if I'm not allowed to ask this question because is has already been asked two years ago, please tell me what to do instead).  Thank you in advance! How can I find and replace specific words in a text file using command line? Resetting theorem counters: \section and (missing) \subsection Let's say we have $x^2=25$ So we have two real roots ie $+5$ and $-5$.  But if we were to differentiate on both sides with respect to $x$ we'll have the equation $2x=0$ which gives us the only root as $x=0$.  So does differentiating on both sides of an equation alter it? If it does, then how do we conveniently do it in Integration by substitutions? If not then what exactly is going on here ? How to change the catcode in a macro Reading Chapter 2 of Koblitz's Introduction to Elliptic Curves and Modular Forms, I got stuck on the following question. I would like to proceed my reading, so I would appreciate any hint to this. I have no background in Algebraic Number Theory, but if someone explains in that language, I would like to see it and learn it as much as I can at this moment. References will also be appreciated!  Let $q$ be a power of prime $p$ such that $q \equiv 1 \mod 4$ and $p \nmid 2n$.  Question. Let $\chi_{4} : \mathbb{F}_{q}^{*} \rightarrow S^{1}$ be the character of order $4$, show that $\chi_{4}(-4) = 1$.  The hint in the book says we may show that $\chi_{4}(4) = \chi_{4}(-1) = 1$ for $q \equiv 1 \mod 8$ and $\chi_{4}(4) = \chi_{4}(-1) = -1$ for $q \equiv 5 \mod 8$.  If $q \equiv 1 \mod 8$, then $\chi_{4}(4) = \chi_{4}(2)^{2} = \chi_{2}(2) = \pm 1$, where $\chi_{j}$ denotes the character of order $j$. So I think $2$ must be quadratic residue in this case, but I cannot figure out why.