Find the difference between the number of rows and columns of a matrix.












0












$begingroup$


Let $B$ be an $n$ by $r$ matrix and let $M$ be the block matrix: begin{pmatrix} 0 &B\ B^t & 0 end{pmatrix}



$M$ has nullity 1. Show that the difference between the number of rows and columns of $B$ is 1.



I am supposed to use the fact that row rank = column rank for matrices over R, however I have no idea where to start.










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  • 2




    $begingroup$
    How are the nullities of $B$ and $B^t$ related?
    $endgroup$
    – user3482749
    Jan 4 at 21:23










  • $begingroup$
    Since their ranks are equal then Null(B)= Null(B^t)+r-n
    $endgroup$
    – John Cox
    Jan 5 at 10:19
















0












$begingroup$


Let $B$ be an $n$ by $r$ matrix and let $M$ be the block matrix: begin{pmatrix} 0 &B\ B^t & 0 end{pmatrix}



$M$ has nullity 1. Show that the difference between the number of rows and columns of $B$ is 1.



I am supposed to use the fact that row rank = column rank for matrices over R, however I have no idea where to start.










share|cite|improve this question









$endgroup$








  • 2




    $begingroup$
    How are the nullities of $B$ and $B^t$ related?
    $endgroup$
    – user3482749
    Jan 4 at 21:23










  • $begingroup$
    Since their ranks are equal then Null(B)= Null(B^t)+r-n
    $endgroup$
    – John Cox
    Jan 5 at 10:19














0












0








0





$begingroup$


Let $B$ be an $n$ by $r$ matrix and let $M$ be the block matrix: begin{pmatrix} 0 &B\ B^t & 0 end{pmatrix}



$M$ has nullity 1. Show that the difference between the number of rows and columns of $B$ is 1.



I am supposed to use the fact that row rank = column rank for matrices over R, however I have no idea where to start.










share|cite|improve this question









$endgroup$




Let $B$ be an $n$ by $r$ matrix and let $M$ be the block matrix: begin{pmatrix} 0 &B\ B^t & 0 end{pmatrix}



$M$ has nullity 1. Show that the difference between the number of rows and columns of $B$ is 1.



I am supposed to use the fact that row rank = column rank for matrices over R, however I have no idea where to start.







linear-algebra linear-transformations






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Jan 4 at 21:17









John CoxJohn Cox

83




83








  • 2




    $begingroup$
    How are the nullities of $B$ and $B^t$ related?
    $endgroup$
    – user3482749
    Jan 4 at 21:23










  • $begingroup$
    Since their ranks are equal then Null(B)= Null(B^t)+r-n
    $endgroup$
    – John Cox
    Jan 5 at 10:19














  • 2




    $begingroup$
    How are the nullities of $B$ and $B^t$ related?
    $endgroup$
    – user3482749
    Jan 4 at 21:23










  • $begingroup$
    Since their ranks are equal then Null(B)= Null(B^t)+r-n
    $endgroup$
    – John Cox
    Jan 5 at 10:19








2




2




$begingroup$
How are the nullities of $B$ and $B^t$ related?
$endgroup$
– user3482749
Jan 4 at 21:23




$begingroup$
How are the nullities of $B$ and $B^t$ related?
$endgroup$
– user3482749
Jan 4 at 21:23












$begingroup$
Since their ranks are equal then Null(B)= Null(B^t)+r-n
$endgroup$
– John Cox
Jan 5 at 10:19




$begingroup$
Since their ranks are equal then Null(B)= Null(B^t)+r-n
$endgroup$
– John Cox
Jan 5 at 10:19










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