Dell T7400 won't boot Ubuntu unless the live USB is connected
Can't boot without Flash Drive plugged in
Proving the geometric sum formula by induction $$\sum_{k=0}^nq^k = \frac{1-q^{n+1}}{1-q}$$  I want to prove this by induction. Here's what I have.  $$\frac{1-q^{n+1}}{1-q} + q^{n+1} = \frac{1-q^{n+1}+q^{n+1}(1-q)}{1-q}$$  I wanted to factor a $q^{n+1}$ out of the second expression but that 1- is screwing it up... How can I prove that every prime except 2 and 5 divide infinitely many of the following integers $11, 111, 1111, ...$ ? Why does Skynet take prisoners? In the Terminator franchise, extermination camps are often mentioned. But from a machine-logic POV, wouldn't it make more sense to just kill all humans on sight, period? Or herd them into small areas and nuke them? (even today's military electronics are hardened against EMPs and Skynet wouldn't care about the environment.)   IIRC, the reasoning behind ghettoization / concentration camps / extermination camps / gas "showers" is to misdirect or mislead people both inside and outside the country as to what was really going on. But Skynet doesn't have to worry about bad publicity, and can manufacture all the free labor it needs. Is there any in-universe explanation for keeping large groups prisoners? Prove that $\mathcal{P}(A)⊆ \mathcal{P}(B)$ if and only if $A⊆B$. Here is my proof, I would appreciate it if someone could critique it for me:  To prove this statement true, we must proof that the two conditional statements ("If $\mathcal{P}(A)⊆ \mathcal{P}(B)$, then $A⊆B$," and, If $A⊆B$, then $\mathcal{P}(A)⊆ \mathcal{P}(B)$) are true.    Contrapositive of the first statement: If $A \nsubseteq B$, then $\mathcal{P}(A) \nsubseteq \mathcal{P}(B)$  If $A \nsubseteq B$, then there must be some element in $A$, call it $x$, that is not in $B$: $x \in A$, and $x \notin B$. Since $x \in A$, then $\{x\} \in \mathcal{P}(A)$; moreover, since $x \notin B$, then $\{x\} \notin \mathcal{P}(B)$, which proves that, if $A \nsubseteq B$, then $\mathcal{P}(A) \nsubseteq \mathcal{P}(B)$. By proving the contrapositive true, the original proposition must be true.    To prove the second statement true, I would implement nearly the same argument, so that isn't necessary to write. So, does this proof seem correct? Also, was the contrapositive necessary? Or is there another way to prove the initial statement? Asked again to review a paper, when the authors don't wish to modify it I have received a manuscript to review for a journal. The interesting thing is, I had already reviewed this article (exact same title, abstract and author list, almost exact same content) for another journal a few weeks ago where I recommended that it be published, but only after major revisions of both form and content. When I first reviewed it, I wrote a two-page review, listing some questions and several “actionable” comments, ranging from some concerns about exactness of the text (some conclusions didn't seem fully backed by the results) all the way down to trivial stuff (grammar, a few typos, graphic issues with the figures, etc.).  Now, the manuscript has come to me for review again, but it is almost unchanged from the first version. None of the serious stuff has been addressed, and even most of the trivial stuff was not fixed (there's at least one remaining typo, and the figures still aren't fully legible). However, I think this behavior from the authors is clearly a bad signal, which should be somehow conveyed to the editor: they're not willing to amend their work, and would rather do some journal-shopping.  What would you suggest me to do? Should I just re-send my earlier review? Add a note to the editor about my knowledge of the “history” of the paper? Or maybe even include it in my review, so the authors are aware that people know of their behavior, and maybe feel bad enough to change their ways?    PS: I wrote it in the present tense, but it's actually a story from my past. I'm not sure I did the right thing at the time, and I think it's better to actually formulate it as an open question… What is the benefit of launching a satellite "a few days before the monthly report" I've seen this hint in the game as well as on this site and I've been wondering if there is any specific advantage to launching satellites closer to the monthly report rather than any time during that month.  The way I see it, monthly maintenance costs are taken out during the reports (correct me if i'm wrong), so regardless of when you launch it during the month it would cost the same.   Is the benefit of holding on to them longer simply a safety net in case some countries go into the red during that time? When going to any page of  with a new reputation gain, the achievements dropdown keeps showing a new badge green highlight:    And then trying to dismiss the notification by clicking on it gets rid of the green badge notification, but the +5 remains even after I've clicked away from the dropdown. Implementing a PIVOT query A fellow player is uncooperative with the group and gets GM favoritism. How do I handle this? I actually have two situations but they are interconnected. Our group is currently playing a Dresden game. The GM and one of the players are married. Along with that, he is a new member to the group. I can understand her (the GM) wanting to make him feel welcome but it has gone into the the realm of blatant favoritism. A few examples:   Every idea he has is deemed fantastic, wonderful, awesome and is always successful. Most of the time he doesn't have to roll to see if he succeeds; he just does. After a series of major setbacks to the other player's characters, I joked that her husband was the only one left to mess with. Her answer to that was that she would absolutely not be messing with him in the game. He and his character were safe from that. In the last session, he and another player had to make the same roll using the same skill for the same information. He needed a fair to succeed. The other player needed a great. Not the first time that has happened.    The second part of this has to do with him as well. As I said, he is new to the group. When we were discussing a game to play, it was made clear that it would be cooperative. We would all be working together to a common end. However, he will not- I mean ever- share any information with the rest of the group. No matter how vital or needed that information is to advance the story, he just smiles and says he's got nothing. To try and get around this problem, a group aspect was created. That way if a situation or information that everybody needed to know came up, a fate chip could be played and anyone who wanted to be a part of it could be present. He is totally abusing it. Now, instead of just not telling us anything, he adds give me a fate chip and maybe I'll tell you something. It's like he is trying to beat us at the game and that is not the way it was set up.    So, the question to these two situations is what do I do? How do I handle this in a rational and sensitive way? To complicate things further, the GM is my best friend. He is her husband. I don't want to put her in the middle but I am about ready to quit the game. I am tired of it being his game and everyone else being bit players. Should I talk to her or should I talk to him? If anyone has had experience with this, any advice would be appreciated. There are a few questions on this forum asking about why Latex3 is taking so long to come out. However, all of these are from the early 2010s. I'm just wondering what the current state of the project is and whether it's ready (or nearly ready) for prime time? When electric dipole placed in non uniform electric field, what is the approach to calculate torque acting on it? Can it be zero? Proving $(A\le B)\vee (B\le A)$ for sets $A$ and $B$ Override a single JavaScript file from a module Incorrect icons on hot network questions I see the same problem has occurred in the past, the most-linked one being   Is this happening for anyone else?   I've marked the icons I could recognize as incorrect.  This exists on every page, is on both chrome and firefox (from Ubuntu 16.04), and persists after hard-refreshes in each.  Edit: The icons in Meta's Hot Network Questions tab appear to be consistently accurate. Every other page I checked (including Unix, Workplace, English Language &amp; Usage, Money, and Sci-fi) have a handful of incorrect ones, even for some of the same questions that are displayed correctly in Meta.  Further note: if it matters, the icons are also incorrect in the drop down community-search feature on the right end of the header. Again, they appear correct on this Meta page, and incorrect on all other pages I've checked. Some of the ones that are consistently incorrect:   computational science constructed languages movies and TV raspberri pi rpg russian language science fiction and fantasy sitecore skeptics super user latex workplace   That distribution seems skewed, but I may just be disproportionately familiar with the sites at the end of the alphabet. Many others could be wrong, those are just the ones I could recognize.    Last edit: apparently my Google skills were lacking -  was asked an hour prior. How can std::make_heap be implemented while making at most 3N comparisons? "I couldn't but laugh" - correct or not? Prove that for any piecewise smooth curve it is possible to find the parametrisation RSA when N=pq and p = q How to get object size in memory? I need to know how much bytes my object consumes in memory (in C#). for example how much my Hashtable, or SortedList, or List&lt;String&gt;. Understanding the length extension attack I have been trying to understand exactly how a length extension attack works on SHA-1. I'll detail below what I've understood so far, so that I can convey my understanding of the same and hopefully get advice on where I'm going wrong.  Lets assume that for a message $m$, a secret $s$ is appended to it and the SHA-1 hash is calculated. If $\textrm{len}(m) + \textrm{len}(s)$ is not a multiple of the block size, a certain amount of padding is added to it to make it a multiple, and the hash is generated using what is essentially $s || m || \textrm{padding}$.  Now SHA-1 internally uses 5 registers — it takes in an block, generates new register values, turns the crank, takes in another block, generates new register values, turns the crank ... and so on till the end. When all blocks are exhausted, the register values are concatenated and spit out.  Assume that an attacker knows a certain value of $m$, for which he also knows the hashed key. In such a case, he knows the state of the 5 registers when $(s || m || \textrm{padding}$ was processed. Lets also assume that the attacker knows the length of $s$, so that he can predict how much padding was added.  Here is where I get confused. From what I've read so far, the attack involves taking the known hash, adding a certain amount of padding and then the value that we want. However, isn't the padding already used up in creating the hash? Why are we using padding in our attack?