Pre isntalled Ubuntu for Dell Vostro 3580 I bought Dell Vostro 3580 with pre-installed Ubuntu 18.04. After some time my hard drive crashes and I installed new hard drive but I can not find original Ubuntu .iso for Dell Vostro 3580 laptop. On Dell site when I enter my service tag number it find my laptop but I can't download original iso. Can anyone help?
(Re?)Install Ubuntu on a Dell laptop that had Ubuntu preinstalled I have Dell Laptop that is 15 5567 7th Generation. So it was maybe pre-installed as Dell says and I can see in the product information that this laptop is Ubuntu built in and based not Windows.  So I want to get my Ubuntu OS again. How can I do that?
If a SHA256 hash with high entropy is then hashed with one made from low entropy, is the resulting hash higher/same/lower entropy? If one were to create a SHA256 hash using 256 coin flips converted to hex (which, as I understand it, is as "entro-phized" as one can capture in SHA256) then take that hash as a string, combine that with a hash of the word "cat" and hash the resulting 512 character string, would the resulting hash from that exercise be any less random than our "perfect" hash we began with?  My thinking is the final string would capture the same amount as the original randomness as what we started with because the "extra" entropy can not be captured and is lost. Is this the case and am I thinking about this correctly? Would hashing something with high entropy with something simpler ever cause a lower amount of randomness or does it only go up?  Thanks to anyone who can help explain this a little better. What's the difference between these two sentences? And which one's grammatically correct? If $x^{2}-x\in Z(R)$ for all $x\in R$, then $R$ is commutative. If $x^{2}-x\in Z(R)$ for all $x\in R$, then $R$ is commutative.  I need to proof this theorem and I have something like this below. However, I do not know how to continue this proof.   $(x+y)^{2}-(x+y)=x^{2}+xy+yx+y^{2}-x-y=(x^{2}-x)+(y^{2}-y)+xy+yx\in Z(R)$  so $xy+yx\in Z(R)$ What is Ambient Occlusion? What is Ambient Occlusion and what are some of it's uses? I see it is used in creating what might be called "shadow catchers" in the following node tree setup: How can I take a picture with my webcam in Windows 7? I know it existed as sort of a folder in Windows Explorer in at least Windows XP, but I just can't seem to find it in Windows 7...  How can I take a picture with my webcam in Windows 7 without using any 3rd party tools? James Paterson in his novel writes, “she was shrink by trade, a forensic profiler, and Jack Morgan’s number two at Private “.   What does whole sentence mean? How can I determine how much bleed to use? How can I check the SMART status of a SSD or HDD on current versions of Ubuntu 14.04 through 20.04? How can I check the SMART status of a drive under 14.04 and beyond? I've seen  but it doesn't seem to apply under 14.04 and later. For example, this regex  (.*)&lt;FooBar&gt;   will match:  abcde&lt;FooBar&gt;   But how do I get it to match across multiple lines?  abcde fghij&lt;FooBar&gt; My question is from Apostol's Vol. 1 One-variable calculus with introduction to linear algebra textbook.  Page 57. Exercise 12. Show that the following are polynomials by converting them to the form $\sum_{k=0}^{m}a_kx^k$ for a suitable $m$. In each case $n$ is a positive integer. $a)$ $(1+x)^{2n}.$ $b)$ $\frac{1-x^{n+1}}{1-x}, x\not=1.$ $c)$ $\prod_{k=0}^{n}(1+x^{2^k}).$  The attempt at a solution: a) part of the problem is pretty easy I guess, it is example of binomial theorem, so the answer would be $(1+x)^{2n}=\sum_{k=0}^{2n}(^{2n}_{k})x^k.$ Answer to part b) would be the following: $$\frac{1-x^{n+1}}{1-x}=\frac{(1-x)(1+x+x^2+\cdots+x^n)}{1-x}=1+x+x^2+\cdots+x^n=‌​\sum_{k=0}^{n}x^k.$$thanks to @DiegoMath's hint. As for part c), we have $$\prod_{k=0}^{n}(1+x^{2^k})=(1+x)(1+x^2)(1+x^4)(1+x^8)\cdots(1+x^{2^n})$$ and I have trouble &quot;converting&quot; this to sum which would be of a form of polynomial. How to restart the networking service? I tried to use  sudo service networking restart   and  sudo /etc/init.d/network restart   but they both crash the window manager and I can no longer use my keyboard for input into X.  when I use the /etc/init.d/ method it complains saying that I should use the service utility  e.g. service networking restart   but it crashes just the same.  Is there a GUI method of restarting networking? I would like to configure my Ubuntu 12.04 server to synchronize its clock with a specific NTP server. Where to set this up? Prove that any complex matrix can be expressed in term of Hermitian and anti-Hermitian matrices How can we prove that any complex matrix can be expressed in term of hermitian and anti-hermitian matrices of the following form $A = H_1 + iH_2$ Where, $H_1$ is hermitian and $H_2$ is an anti-hermitian matrix Why is homology invariant under deformation retraction/homotopy equivalence? Every time I open a folder from the desktop, a prompt is shown that the said folder is opened. How do I stop that? How to check if running on UI thread in Android? "To delete" is to "deletion" as "to discard" is to what? "To delete" is to "deletion" as "to discard" is to what? Setup IIS 7.5 with multiple website bindings and SSL? On IIS 7.5 I am trying to achieve this with two websites:  Default Web Site is bound to:  (blank host header port 80 - http) (blank host header port 443 - https) go.example.com www71.example.com the IP address of go.example.com  2nd web site "Beta" is bound to:  beta.example.com (blank host header port 443 - https) * using blank only because it doesn't seem to be possible to    bind https to a named host header   And both need to work with SSL.  But I have these problems:   When I type in beta.example.com, I see the go.example.com site instead I can not seem to add the SSL binding to both websites at once (I have a single *.example.com wildcard certificate).  The beta site will not even start if I add the https binding to it.   This is how I have set it up:    What is the correct way to set it up? Update Migration Path List for Non-Moderators Finding an isomorphic subring of matrices