I am entering the correct password in Ubuntu, but the screen just blinks and again shows me the same login screen. Guest session works properly. What should I do?
My Ubuntu is stuck in a login loop when trying to enter my desktop. When I login, the screen gets black and soon after that the login screen comes back.   I've read that the problem might be caused by an error depending on the graphics, here's my graphics card: ATI Radeon 7670M
How do I pre-install Ubuntu for someone (OEM install)? Why does an argument similiar to 0.999...=1 show 999...=-1? How do i prove invertibility of this linear transformation Let $T$ be a linear transformation from a vector space $V$  over reals into $V$ such that $T-T^2=I$. Show that $T$ is invertible I have come across a question about determining possible minimal polynomials for a rank one linear operator and I am wondering if I am using the correct proof method.  I think that the facts needed to solve this problem come from the section on Nilpotent operators from Hoffman and Kunze's "Linear Algebra".     Question: Let $V$ be a vector space of dimension $n$ over the field $F$ and consider a linear operator $T$ on $V$ such that $\mathrm{rank}(T) = 1$.  List all possible minimal polynomials for $T$.   Sketch of Proof:   If $T$ is nilpotent then the minimal polynomial of $T$ is $x^k$ for some $k\leq n$.  So suppose $T$ is not nilpotent, then we can argue that $T$ is diagonalizable based on the fact that $T$ must have one nonzero eigenvalue otherwise it would be nilpotent (I am leaving details of the proof of diagonalization but it is the observation that the characteristic space of the nonzero eigenvalue is the range of T and has dimension $1$).  Thus the minimal polynomial of $T$ is just a linear term $x-c$.    Did I make a mistake assuming that $T$ can have only one nonzero eigenvalue?  Thanks for your help How to evaluate this trigonometric limit? I have been struggling to solve this limit.  What is the limit as $x$ approaches $45^0$ of $$\frac{\sqrt{2}\cos x-1}{\cot x-1}?$$   I know how to use L'Hospital's rule to calculate this limit and got the answer as $0.5$. But, how do I calculate the limit by manipulating the function? Please provide only some hints to proceed. How do I solve this limit: $\lim _{x \to 0} \left(\frac{ \sin x}{x}\right)^{1/x}$? Why do gases have weight? I know that a gas is made of atoms or molecules moving freely in space.  When these particles hit the walls of where they're kept in they cause something called pressure.  But these particles never pile up on each other and push a surface down by their weight so that we can measure it as weight, not pressure.  So why do gases have weight? Is Einstein's Special Relativity completely inclusive of Newton's 3 laws of motion? Relativity has always been explained to me (in books I've read, etc) as a superset of newton's laws - that is; it encapsulates all of Newton's mechanics in addition to other effects (observer effect, time dilation, space-time geometry, etc).   I can kind of imagine 2 of Newton's 3 laws of motion to be incapsulated within Einstein's Special Relativity, but the one about "for every action there is an equal and opposite reaction", I'm struggling to find a place for that within Special Relativity.   Does this sit outside Special Relativity's explanatory power or is it inferred within somehow? Settings API enable default settings on theme install? I am still learning settings API so please forgive my noob question. I have three fields: a checkbox, colorpicker and text field (they are working), but I would like to do this: when the theme is installed add "checked" state to my checkbox but allow user to "unchecked" it ,and if empty add default color to my colorpicker... I have no idea how to do this so please help me!  My code looks like this now (thanks to @Chip Bennett! ) :  &lt;?php add_action('admin_menu','create_theme_options_page'); function create_theme_options_page(){ add_options_page('Theme Options','Theme Options','administrator',__FILE__,'build_options_page'); }    function build_options_page(){    ?&gt;    &lt;div id="theme-options-wrap"&gt;    &lt;div style="float:left;margin-top:19px;position:absolute;" class="icon32" id="icon-tools"&gt;&lt;br/&gt;&lt;/div&gt;    &lt;h2&gt;My options page&lt;/h2&gt;    &lt;form method="post" action="options.php"&gt;    &lt;?php settings_fields('plugin_options');?&gt;    &lt;?php do_settings_sections(__FILE__); ?&gt;    &lt;p class="submit"&gt;    &lt;input name="Submit" type="submit" class="button-primary" value="&lt;?php esc_attr_e('Save changes');?&gt;"/&gt;    &lt;/p&gt;    &lt;/form&gt;    &lt;/div&gt;    &lt;?php    }       add_action('admin_init','register_and_build_fields');      function register_and_build_fields(){      register_setting('plugin_options','plugin_options','validate_setting');      add_settings_section('main_section','&lt;br/&gt;&lt;br/&gt;Main Settings','section_cb',__FILE__);      add_settings_field('banner_heading','Banner Heading:','banner_heading_setting',__FILE__,'main_section');      add_settings_field('display_sidebar','Display Sidebar:','display_sidebar_setting',__FILE__,'main_section');      add_settings_field('display_colorpicker','Display Colorpicker:','display_colorpicker_setting',__FILE__,'main_section');      }        //Install Iris colorpicker        add_action( 'admin_enqueue_scripts', 'mw_enqueue_color_picker' );        function mw_enqueue_color_picker( $hook_suffix ) {        // first check that $hook_suffix is appropriate for your admin page        wp_enqueue_style( 'wp-color-picker' );        wp_enqueue_script( 'my-script-handle', get_template_directory_uri() . '/js/my-script.js', array( 'wp-color-picker' ), false, true );        }           //Colorpicker          //Now how to add a default color on theme install?          function display_colorpicker_setting(){          $options = get_option('plugin_options');          echo"&lt;input type='text' id='color1' name='plugin_options[display_colorpicker]' value='{$options['display_colorpicker']}'/&gt;";          }            //Sidebar checkbox           //Now how to add a default state "checked" on theme install?           function display_sidebar_setting(){           $options = get_option('plugin_options');           echo "&lt;input type='checkbox' name='plugin_options[display_sidebar]' {$options['display_sidebar']} id='display_sidebar' /&gt;";           }              //Banner Heading             function banner_heading_setting(){             $options = get_option('plugin_options');             echo "&lt;input name='plugin_options[banner_heading]' type='text' value='{$options['banner_heading']}'/&gt;";             }               //Validate our settings here               function validate_setting($plugin_options){                  return $plugin_options;               }                 function section_cb(){                } ?&gt; I am trying to solve the following two problems:  1) Prove that the functions $\cos(z)$, $\sin(z)$ are surjective over the complex numbers.  2) Find all $z \in \mathbb C$: $cos(z) \in \mathbb R$ and find all $z \in \mathbb C$: $\sin(z) \in \mathbb R$.  For 1),I've tried to prove it for the function $\cos(z)$ (I suppose the other one is analogue)  so I've used the fact that $\cos(z)=\dfrac{e^{iz}+e^{-iz}}{2}$.  Let $w \in \mathbb C$, I want to show there exists $z \in \mathbb C : f(z)=w$, i.e., $\dfrac{e^{iz}+e^{-iz}}{2}=w$, multiplying by $2$ and then by $e^{iz}$ yields $e^{2iz}+1=2we^{iz}$ iff $e^{2iz}-2we^{iz}+1=0$.   I don't know if this approach is the correct one but here I've replaced $e^{iz}$ by $x$, so the solutions of the equation would be the roots of the polynomial $p(x)=x^2-2wx+1$, by the quadratic formula, I get that $x \in \{\dfrac{2w+w_0}{2},\dfrac{2w-w_0}{2}\}$, where $w_0^2=4w^2-4$.  Then, $e^{iz} \in \{\dfrac{2w+w_0}{2},\dfrac{2w-w_0}{2}\}$. At this point I got lost, I would like to explicitly show that $z$ exists and I can't see existence directly from the fact that $e^{iz}=\dfrac{2w+w_0}{2}$ or $e^{iz}=\dfrac{2w-w_0}{2}$.  First I thought of taking logarithm of both sides of the equation ir order to solve for $z$, but this is not a legitimate operation unless $e^{iz} \in \mathbb R$.   I couldn't go any farther.  For point 2) I have no idea what to do, should I use the identity $\cos(z)=\dfrac{e^{iz}+e^{-iz}}{2}$?  I would appreciate some help with the two points (specially with point 2), at least in 1) I could do something).   Btw, Happy new year! Value of $\frac{x^n -a^n}{ x-a}$? Recently I've noticed more and more sign-in / sign-up workflows defaulting to the sign-up option first and providing a minimal "Sign-In / Login" action somewhere else on the page. What's the reason behind this practice?  Examples where I've seen this recently: KeyboardViewer app is saved from this AppleScript.  on run {input, parameters}     if application "KeyboardViewer" is running then         quit application "KeyboardViewer"     else          activate application "KeyboardViewer"     end if     return input end run   Dock toggle save. Adding shortcut to above, needs some work...   Syntax error Can’t set application "KeyboardViewer" to some object. Access not allowed.  tell application "System Events"     set application "KeyboardViewer" to (keystroke "K" using control down) end tell Show that $a_{n+1}= 1 + \frac{1}{a_n}$ converges. How can I concatenate two arrays in Java? I need to concatenate two String arrays in Java.  void f(String[] first, String[] second) {     String[] both = ??? }   What is the easiest way to do this? Does $x^2 - y^2 = 12345678$ (x,y are integers) have any solutions? This question appeared in KVPY online exam held on Nov 5. This equation is the equation of a hyperbola so any solution must be of the form $a\sec(k),a\tan(k)$. So no solutions. Zooming to selection in arcpy.mapping and only seeing selected features? I selected data by using select layer by attribute, then I need to only select these selection and zoom in to the selection.  my code is this, it can zoom in base on the scale I set, but I see other adjacent polygon that has other Code_No, why?  Layer = arcpy.mapping.ListLayers(mxd, "lyr", df)        arcpy.SelectLayerByAttribute_management(lyr, "NEW_SELECTION", "Code_NO = '%s'"%mycodeNo)            df.extent = lyrLayer1.getSelectedExtent() df.scale *= 2 If $|\lbrace g \in G: \pi (g)=g^{-1} \rbrace|>\frac{3|G|}{4}$, then $G$ is an abelian group. Assume that $\pi$ is an automorphism of a finite group $G$. Let $S$ denote the set $\lbrace g \in G: \pi (g)=g^{-1} \rbrace$. Show that if $|S|&gt;\frac{3|G|}{4}$, then $G$ is an abelian group.    Anyone has any idea on how to solve this ? I have no idea how to start. How to know number of cores of a system in Linux? I wanted to find out how many cores my system has, so I searched the same question in Google. I got some commands such as the lscpu command. When I tried this command, it gave me the following result:  $ lscpu Architecture:          x86_64 CPU op-mode(s):        32-bit, 64-bit Byte Order:            Little Endian CPU(s):                4 On-line CPU(s) list:   0-3 Thread(s) per core:    1 Core(s) per socket:    4 Socket(s):             1 NUMA node(s):          1 Vendor ID:             GenuineIntel CPU family:            6 Model:                 23 Stepping:              10 CPU MHz:               1998.000 BogoMIPS:              5302.48 Virtualization:        VT-x L1d cache:             32K L1i cache:             32K L2 cache:              2048K NUMA node0 CPU(s):     0-3   In particular, this output shows:   CPU(s): 4 Core(s) per socket: 4 CPU family: 6   Which of those indicates cores of a Linux system?  Is there any other command to tell the number of cores, or am I assuming it is completely wrong? Timeout for Always On Synchronous Commit Mode For SQL Server Enterprise's Always On availability groups, how can you configure the timeout for Synchronous Commit mode?  Is there a maximum?  Can it work, for example, between continents? Thanks