Prove that the following determinant equals 0












2












$begingroup$


We have a $n*n$ matrix $A=(a_{i,j})$.
If $i=j$, then $a_{i,j}=1-n$. otherwise, $a_{i,j}=1$. Show that $|A|=0$.
I tried using gauss elimination but it just gets too complicated. I also tried to do $R_i rightarrow R_i-R_1/(1-n)$ for all $i>1$, and then expand over the first column, but it also didn't work for me. Can someone please help?










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    2












    $begingroup$


    We have a $n*n$ matrix $A=(a_{i,j})$.
    If $i=j$, then $a_{i,j}=1-n$. otherwise, $a_{i,j}=1$. Show that $|A|=0$.
    I tried using gauss elimination but it just gets too complicated. I also tried to do $R_i rightarrow R_i-R_1/(1-n)$ for all $i>1$, and then expand over the first column, but it also didn't work for me. Can someone please help?










    share|cite|improve this question









    $endgroup$















      2












      2








      2





      $begingroup$


      We have a $n*n$ matrix $A=(a_{i,j})$.
      If $i=j$, then $a_{i,j}=1-n$. otherwise, $a_{i,j}=1$. Show that $|A|=0$.
      I tried using gauss elimination but it just gets too complicated. I also tried to do $R_i rightarrow R_i-R_1/(1-n)$ for all $i>1$, and then expand over the first column, but it also didn't work for me. Can someone please help?










      share|cite|improve this question









      $endgroup$




      We have a $n*n$ matrix $A=(a_{i,j})$.
      If $i=j$, then $a_{i,j}=1-n$. otherwise, $a_{i,j}=1$. Show that $|A|=0$.
      I tried using gauss elimination but it just gets too complicated. I also tried to do $R_i rightarrow R_i-R_1/(1-n)$ for all $i>1$, and then expand over the first column, but it also didn't work for me. Can someone please help?







      linear-algebra determinant






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      asked 2 hours ago









      OmerOmer

      2908




      2908






















          1 Answer
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          7












          $begingroup$

          Hint:$$
          Aleft(begin{array}{c}1\1\vdots\1end{array}right)=0.
          $$






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            1 Answer
            1






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes









            7












            $begingroup$

            Hint:$$
            Aleft(begin{array}{c}1\1\vdots\1end{array}right)=0.
            $$






            share|cite|improve this answer









            $endgroup$


















              7












              $begingroup$

              Hint:$$
              Aleft(begin{array}{c}1\1\vdots\1end{array}right)=0.
              $$






              share|cite|improve this answer









              $endgroup$
















                7












                7








                7





                $begingroup$

                Hint:$$
                Aleft(begin{array}{c}1\1\vdots\1end{array}right)=0.
                $$






                share|cite|improve this answer









                $endgroup$



                Hint:$$
                Aleft(begin{array}{c}1\1\vdots\1end{array}right)=0.
                $$







                share|cite|improve this answer












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                share|cite|improve this answer










                answered 2 hours ago









                SongSong

                7,991423




                7,991423






























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