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$ \int_{0}^{ \infty} \int_{0}^{ \infty} \frac { e^{-(x+y)}}{x+y} dx dy $ Question : The integral   $$ \int_{0}^{ \infty} \int_{0}^{ \infty} \frac { e^{-(x+y)}}{x+y} \mathop{dx}\mathop{dy} $$  is   (a) infinite   (b) finite but can not be evaluated in closed form   (c) 1  (d) 2 .  I tried substituting $u=x+y$ and $v=y$ that led me no where . I'm not even sure about convergence of integral .Any help would be greatly appreciated . Is there such a thing as a restore point in Ubuntu? Windows has this. Basically what I want is to record the state of the system either manually or periodically and then restore to that point if required. For example, before upgrading the distribution, or before installing a certain package.  What would be the easiest way to do this? Here is a picture of two of them:    I searched for these connectors in  and  for an hour, but couldn't find anything similar. Can you please name these connectors for me and/or give a link to their subcategory in one of these part seller websites? Indefinite Integral with "sin" and "cos": $\int\frac{3\sin(x) + 2\cos(x)}{2\sin(x) + 3\cos(x)} \; dx $ Mixed DML operation error I am facing Mixed DML error in the following case:  static testmethod void method1() {     User u1 = DataFactory.createUser('testUser','test@user.com','permissionSetAPIname');        Obj1 rec1 = DataFactory.createrec1('Record1');     insert rec1;      Obj2 rec2 = DataFactory.createrec2('Rec2',rec1,system.today()-10, system.today()+10 );     insert rec2;       Obj3 rec3 = DataFactory.createrec3(rec2,'Tester',u1,'US');     insert Role;      test.starttest();         //testing code      test.stoptest();  }   However the following is working fine  static testmethod void method1() {      User u1 = new User(Alias = 'testRole',                   Email             = 'role@test.com',                   EmailEncodingKey  = 'UTF-8',                   LastName          = 'user',                   FirstName         = 'test',                   LanguageLocaleKey = 'en_US',                   LocaleSidKey      = 'en_US',                   ProfileId         = [select Id from Profile where Name = 'Basic User' limit 1].Id,                   TimeZoneSidKey    = 'America/Chicago',                   Username          = 'stakeholder@test' + Math.round(Math.random() * 10000) + '.com',                   UserRoleId        = null,                   Country           = 'Great Britain');     insert u1;         Obj1 rec1 = DataFactory.createrec1('Record1');     insert rec1;      Obj2 rec2 = DataFactory.createrec2('Rec2',rec1,system.today()-10, system.today()+10 );     insert rec2;       Obj3 rec3 = DataFactory.createrec3(rec2,'Tester',u1,'US');     insert Role;      test.starttest();         //testing code      test.stoptest();  }   Please explain the difference. As my understanding is that transaction remains the same in both the cases. I have heard rumors that you can compile documents online, and more specifically that Google has a free online compiler, but I have never been able to find any. Is there a way to compile documents online, so that I can write and compile documents even if I don't have a TeX distribution installed on my computer? Story featuring smart people sent on a space mission to nowhere The story in question featured, as the vague title suggests, a "space mission" that is really a cover for forcing a bunch of really smart people to be in close proximity to each other for long enough that they can truly evolve their collective intelligence. I recall them developing new maths and, e..g, "farseeing" and eventually figuring out that while there was no planet at the end of their journey as they were told, they were able to construct one for themselves. How can I set the drawableRight resource via code? Would Gravitational Time Dilation still apply between two gravitational sources? As explained on , when an object is experiencing strong gravitational forces, time passes slower for it. If, in theory, you had two objects exerting the same amount of gravitational pressure on an object in opposite directions, effectively cancelling each other out, would they cancel out the time dilation, or would they compound, making the time dilation more prevalant? Producing doc/docx from LaTeX Is there any way to produce doc/docx files from LaTeX? A doubt from Milnor's "Topology from a Differentiable Viewpoint". This is a doubt from Milnor's "Topology from a Differentiable Viewpoint".     For a smooth $f:M\to N$, with $M$ compact, and a regular value $y\in N$, we define $n(f^{-1}(y))$ to be the number of points in $f^{-1}(y)$. It is easy to see that $n(f^{-1}(y))$ is finite. It can also be seen that $n(f^{-1}(y))$ is locally constant; i.e. there is a neighbourhood of $y$ such that for every point $y'$ in that neighbourhood, $n(f^{-1}(y'))=n(f^{-1}(y))$.   The proof for the statement in bold is the following:     Let $x_1,x_2,\dots,x_n$ be the points of $f^{-1}(y)$, and choose disjoint neighbourhoods $U_1,U_2,\dots,U_n$ of these points, which are mapped diffeomorphically into neighbourhoods $V_1,V_2,\dots,V_n$ of $y$. The required neighbourhood is $(V_1\cap V_2\cap\dots V_n)-f(M-U_1-U_2-\dots U_n)$.   I don't understand how $(V_1\cap V_2\cap\dots V_n)-f(M-U_1-U_2-\dots U_n)$ is open. I know that $(V_1\cap V_2\cap\dots V_n)$ is open. However, how can one prove that $f(M-U_1-U_2-\dots U_n)$ is closed? I can see this working if $f$ is surjective, but not otherwise. My brother owns Skyrim on steam. We use Steam Family Share, but we were wondering how both of us could play it at the same time? When can we use 'much' in affirmative clauses? I found the below in  web-site:     We use much in questions and negative clauses to talk about degrees of something.      We don’t use much in affirmative clauses.   Also, it the same web-site, I found the following:     She runs much faster than he does.    also I noticed that some web-sites use much with affirmative clauses:     May we all be having this much fun and getting this much exercise when we're his age!    Is it Okey to use much in affirmative clauses? If yes, when can we use it? and what is the rules?  Update:  Here is another example on how often the word "much" is used  in informal style:     After much consideration I will NOT be performing at the Inauguration with my improv group Capitol Hill-arious How to adjust the breaking in the bibliography? Is it considered normal to publish job offers inviting candidates to apply based on their gender and/or race in academia? I was browsing PhD position offers in Europe on different websites and I was quite surprised to find that several offers contained sentences such as     University of X value equality and diversity. We strongly encourage women and BAME applicants for this position.    where BAME stands for Black, Asian and Minority Ethnicities; or     The research group aims to increase the number of women in scientific positions. Female candidates are therefore encouraged to apply.   Is it considered normal in the academic environment to discriminate between  candidates according to their race and/or gender for "egalitarian" reasons?   How is the choice of a candidate based on their gender and/or race considered "egalitarian"? Is Adzerk safe / legitimate? Is it (and if yes how?) possible to define an an binary operation $*$ for an arbitrary set $M$ such that $(M,*)$ is a group?  If $M$ is finite or countable infinite this is trivial, but is it also possible for any other sets? And if yes how can you construct $*$? If no can you provide a counterexample? How can I add a class to a block with code (development) For theming reasons I'd like to add a specific class at the "block" level to some of the blocks I'm generating with a custom module. I know there is a module , but I would rather like to do it directly in code (there is no need to change is afterwards).   I also know of , but that does not seem to allow adding or editing classes.  Is it possible to add a class with to a block from within my module code? I'm using Drupal 7. I've implemented AStar in Java and it works ok for an area with obstacles where the chosen destination is reachable.  However, when the destination is unreachable, the calculated "path" is in no way to the closest location (to the unreachable location) but is instead some random path.  Is there a feasible way to tweak AStar into finding the path to the closest location to an unreachable destination? What does "proverbial" mean?