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It is asked to solve the PDE  $$u_x + u_y + u = e^{x+2y}$$  My attempt: We have that $$\frac{dx}{1}=\frac{dy}{1}=\frac{du}{e^{x+2y}-u} $$  $\Rightarrow \frac{dy}{dx}=1 \Rightarrow y=x+C_1 \iff C_1=y-x$  $\Rightarrow \frac{du}{dx}= e^{x+2y}-u \iff \dot{u}+u=e^{x+2y} \iff \\ \frac{d}{dx}(e^x u) = e^{2x+2y} \iff u = e^{-x} ( \frac{1}{2}e^{2x+2y} + C_2)$  As $u$ is constant along its characteristics:  $$u(x,y)=\frac{e^{-x}}{2}(e^{2x+2y} + 2C_2(y-x))$$  where $C_2$ is any function of one variable. But wolfram gave the following answer  $$u(x,y)=\frac{e^{-x}}{4}(e^{2x+2y} + 4C_2(y-x))$$  as you can check   What am I doing wrong? I just finished backing up my system and when I try to upgrade to Utopic Unicorn, I get the error "Cannot Calculate the upgrades." I ran the upgrade by sudo apt-get dist-upgrade, sudo do-release-upgrade after the GUI method failed, they all gave the same error.  The feedback gives some recommendations:  This can be caused by:  * Upgrading to a pre-release version of Ubuntu  * Running the current pre-release version of Ubuntu  * Unofficial software packages not provided by Ubuntu    I am not upgrading to a pre-release version nor coming from one, I'm going from Ubuntu 14.04 LTS to 14.10. I have no broken packages and I have unchecked all my non-official software sources in the 'Software &amp; Updates' manager.  My guess left is the Unofficial software packages not provided by Ubuntu. If anyone could give any help as to how to check for unofficial packages using Synaptic or another, my appreciation.  Are there any other factors that may be causing this error and how would I go about checking/fixing those?  Thanks.  Edit: I have no broken or held packages. Everything is up-to-date, and restarting everything or anything has no effect. Show that holomorphic $f_1, . . . , f_n $ are constant if $\sum_{k=1}^n \left| f_k(z) \right|$ is constant. While studying for an exam in complex analysis, I came across this problem. Unfortunately I was not able to solve it. Any help would be greatly appreciated.  Let $U ⊂ \mathbb{C}$ be a domain and $f_1, . . . , f_n : U \rightarrow \mathbb{C}$ holomorphic functions, such that $\sum_{k=1}^n \left| f_k(z) \right|$ is constant on $U$. Show that $f_1, . . . , f_n$ are constant. Emails Per Invocation Still Capped at 100? Any way to add CSS for a single page/node? I'm cleaning up my big crazy style sheets (possibly pertinent to a future question) and I'm wondering the best way to add custom CSS to a specific node or page. In particular, my work site's home page is a Panel Page and it has a bunch of different styling. Right now the CSS is just included with the main theme style sheet. Is there a way to say, &quot;if this is node Foo, then add foo.css&quot;? Is  what I'm looking for? I might be interested in generalizing this to other nodes/sections/etc, but at the moment I just want to handle this one item. Reattach to lost X11 session I'm using X11 forwarding over ssh to run Linux apps on my Windows box, and when the network drops it loses everything that was running. Is there anything similar to screen for X11? My book tells me that of the solutions to the Lagrange system, the smallest is the minimum of the function given the constraint and the largest is the maximum given that one actually exists.  But what if we only have one point as a solution? How to know whether Lagrange multipliers gives maximum or minimum? How to change row color based on a single cell's value? Possible Duplicate:          I have a spreadsheet where I have cell within a row that will contain specific text via data validation. So for instance a cell could contain the text "Due in 7 Days", "Past Due", or "Closed".  I want the row color to change depending on the text that appears in the cell. So if the text "Past Due" appears in the cell I want that entire row to turn red, if "Due In 7 Days" appears the row should turn yellow, and if "Closed" the row would turn gray.  How can I do that? How to print without newline or space? Do PhD courses in engineering fields in European non-English speaking countries require knowledge of the native language? Can a Ph.D. student who only knows how to speak English study in a European non-English speaking country (e.g., Austria, Netherlands, Switzerland, Italy, etc.)  without any problems? Does applying to these universities require knowledge of that country's language? It seems to me that tuples are just as elementary as sets. Can tuples be reduced to sets? Strip whitespace from jsp output Simple Past vs. Present Perfect: "was" vs. "has been" Possible Duplicate:          As a English non-native speaker it is difficult for me to understand when I must use present perfect or past simple because in my official language there isn't the present perfect tense. I know that present perfect is related to something that happened in the past but its result is important now. But for instance:        The message has been sent.   The message was sent.      Please help me point me out any examples/contexts where I should use 1. instead of 2. I guess I can live with the fact that the  changes size drastically when he transforms, but why does his shirt rip off and not his pants?  I think that we need a little better answer than "it keeps us tied to the fact that inside he's still human". I am stuck with the following problem.     Prove that $$\limsup_{n \to \infty} (a_n+b_n) \le \limsup_{n \to \infty} a_n + \limsup_{n \to \infty} b_n$$   I was thinking of using the triangle inequality saying $$|a_n + b_n| \le |a_n| + |b_n|$$ but the problem is not about absolute values of the sequence.  Intuitively it's clear that this is true because $a_n$ and $b_n$ can "reduce each others magnitude" if they have opposite signs, but I cannot express that algebraically...  Can someone help me out ? I have 4GB RAM. When I open Firefox, IntelliJ IDEA or VS Code and some other application my memory is about used up thus my machine hangs and I can't do anything. I can't even close any applications.    Date and time are shown in the top bar so that I can view it any time without any thing typing.   If I would view memory status in this way without typing anything then I can make a decision whether to open an application or whether this application may put my machine in hanging state or not.    Is it possible in Ubuntu 18.04 LTS? iPhone Passcode for Powering Off Did Harry Potter lose Voldemort's powers when he lost his connection to Voldemort? Harry noted to Dumbledore that he had a number of things in common with Voldemort. And it was later revealed that some of Voldemort's power was transferred to Harry when Voldemort tried to kill him. So, what powers did Harry get from Voldemort (i.e. Parseltongue and others) and did they all leave him when he stopped being a horcrux?    Update In the Chamber of Secrets Dumbledore states that Harry has many qualities that Salazar Slytherin values in his hand picked students. Parseltongue - resourcefulness - determination - a certain disregard for rules.    So, does anyone know what specific powers Harry got from Voldemort and is there anyway to tell if he lost anything else besides Parseltongue? Lie algebra of $\left(\begin{smallmatrix}a & b\\ & a^2\end{smallmatrix}\right )$ in $GL_2(\mathbb{R})$ Is it time for Stack Exchange, Inc and the community to legally separate amicably?