Is it right to tell        Five years ago he already knew that two plus two equals four.      or        Five years ago he already knew that two plus two equaled four.      ?  On English classes (I live in not English speaking country) we have learnt that if present clause is dependent to past one than it turns into past. However, I did not fully agree with it and gave (the top sentence above as) an example. It caused a lot of confusion.  In my country's official pre-university English exams (one of the previous years' variants) there is a text with tasks. One of the sentences is:  Nurse believed that fresh air and food ____ very important in fighting soldiers' diseases. A. are B. were ...   I was really surprised when I discovered that the right answer is B. were.  My logic is: when nurse dies, it won't become unimportant. That's why A. are should be right.  Could someone please help figuring it out?
For example:  "Last week, I found out that NASA stands for 'National Aeronautics and Space Administration.'"  or  "Last week, I found out that NASA stood for 'National Aeronautics and Space Administration.'"
TikZ or cryptocode package for cryptographic protocol diagrams Composite primary key from multiple tables / multiple foreign keys I want to build a composite primary key made up of foreign keys from two different tables. I'm still pretty green to this...  A great answer was given to building a composite key from multiple foreign keys on  but I want to do this from multiple tables. I am using Oracle 11g.  foreign key (Name, BoughtFrom, TimeBought)    references the_other_table_name (Name, BoughtFrom, TimeBought)   Imagine that the "references" line actually includes multiple tables. I'm not even sure that the above syntax will work with Oracle.  I have one table "Student" and one table "Parent". It is a many-to-many relationship. My association table is named "Relation" and I would like to make a composite primary key from "PAR_ID" and "STU_ID". Both are foreign keys. Calculus Question: $\int_0^1\frac{(x-x^2)^4}{1+x^2}dx$ Installed MySQL but still says command not found I downloaded MySQL's rpm bundle from the site, converted it to a .deb file using alien and installed it by saying sudo dpkg -i mysql-server_5.6.14-2_amd64.deb. However, when I say mysql in the command line, it gives an error that it is not installed. What do I do?  I am on Ubuntu GNOME 13.10 64-bit How did Harry become a Horcrux? How Can I View All The Reputation Gained/Lost For One Specific Question If I would like to view all of the reputation I have gained or lost due to one specific question of my own, how can this be done?  Is it possible for someone with, say, 421 rep on the site in question? What is an intuitive explanation of the Hopf fibration and the twisted Hopf fibration? As the question suggests, what is an intuitive explanation of the Hopf fibration and the twisted Hopf fibration? Many thanks in advance. Is it possible to follow a user automatically? While the etiquette of dealing with duplicate answers , there hasn't been a great way to deal with these, "Uh, yeah, I said this, too" types of behavior than the almighty downvote.   It would be nice to have a "Duplicate Answer" option on the flag menu. Five flags auto-deletes the answer, as with any other flag. In order to prevent abuse, the flagged answer would have to have the last owner edit (including original post) be younger than the original answer's original posting by at least 2 minutes.  Also, this ability should be a 5,000+ rep privilege, since we currently have no fanfare of rep from 3,001 to 9,999, and a power like this has a bit more umph than closing a question.  Thoughts? This question follow's JeffE's comment :     In most industries, a PhD has negative value.   I am curious about what potential negatives there may be with having a PhD, particularly in industries.  For example, my PhD has applications for image sensors, and the potential of working in that field is appealing—would having a PhD be a potential barrier? Would it be a case of how explicit the practicalities of the PhD can be made?  Would this make any difference? Alternatives to "and/or"? As a programmer, I have no problem with seeing or using "and/or" in technical documentation. For example,     I can upvote an answer that satisfies me and/or mark it as accepted.   That's perfectly good English to me. However, if I were writing a novel, or even just an essay, or — heaven forbid — a poem, "and/or" would seem extremely out of place.  My question is, what should I be using instead? (I solemnly swear I will not use that knowledge to actually write a poem.) I would like to customize Ubuntu live CD by installing some additional packages. I have followed   but it doesn't seems to work. Can anyone provide clear instructions?   Note: I do not prefer Remastersys, manual way will be appreciated.  Customization  Packages that I want to install:   Thunderbird    Samba    SSH       Changes that I need:   Remove Games menu from the Application menu Firefox shortcut on Desktop Radiance as the default Theme Different default Ubuntu Wallpaper   Configuration file changes   I want the panel to be placed at the bottom I want to paste my Samba configuration file instead of default Samba configuration I have few Firefox shortcuts and folders I would like to show that in Desktop Also it will be nice if you say me how to change the icon sets   Recent Updates   I have customized Ubuntu 10.10 with Firefox shortcuts and few folders on desktops. Everything went smooth. But the installer gets crashes after choosing the timezone. How do i fix this issue? Also setting wallpaper affects the login screen. The wallpaper which i set is displayed on the login screen also. I just want the default one for the login screen. Who are all of the companions and how do I get them? How to force Logger.debug output in Play! framework specs2 tests? Where can I safely store my stuff? I would like to know how many switch can be stacked with fiber channel to get a best transfer rate between computers.  I have 200 computers connected to 12 3Com switches. All switches have two fiber ports.  Is the best way to have fiber backbone switch and connect fiber channel from every switch to the backbone? Or connect switch 1 to switch 2 to switch 3 to ... switch 12 to switch 1 again?  Thanks! What's the difference between TRUNCATE and DELETE in SQL What's the difference between TRUNCATE and DELETE in SQL?  If your answer is platform specific, please indicate that. I will quote a question from my textbook, to prevent misinterpretation:     Let $G$ be a finite abelian group and let $m$ be the least common multiple of the orders of its elements. Prove that $G$ contains an element of order $m$.   I figured that, if $|G|=n$, then I should interpret the part with the least common multiple as $lcm(|x_1|,\dots,|x_n|)=m$, where $x_i\in G$ for $0\leq i\leq n$, thus, for all such $x_i$, $\exists a_i\in\mathbb{N}$ such that $m=|x_i|a_i$. I guess I should use the fact that $|x_i|$ divides $|G|$, so $\exists k\in \mathbb{N}$ such that $|G|=k|x_i|$ for all $x_i\in G$. I'm not really sure how to go from here, in particular how I should use the fact that $G$ is abelian. Let $G$ be a group and $c\in G$. Define $*$ on $G$ by: $x*y=xdy$ for all $x,y\in G$, where $d$ is the inverse of $c$. Prove $(G,*)$ is a group. Let $G$ be a group and $c$ be a fixed element of $G$. Define a new operation $*$ on G by:   $$x*y=xdy$$   for all $x$ and $y$ in $G$, where $d$ is the inverse of $c$. Prove that $G$ is a group under the operation $*$.    If you want to check, this problem is in the book “A Course In Group Theory”, by John F. Humphreys (problem $3$, page $28$)   I know what are the axioms that $(G,*)$ must obey in order to be a group and I did show that all the axioms where obeyed except the inverse axiom.  My problem is that, whenever I try to verify what would the inverse be for some element $x$, I get an equation where the $x$ is cancelled in both sides.  Can please someone guide me?  Thank you!  (P.S.: This is NOT a homework assignment, I’m studying Group Theory by this book and got problems solving this question) Why can current only flow in loops? In the following image:   Why can't current flow across the following wire? It's a simple question, but I've kind off always wondered.  Thanks!