What is the meaning of Rank[A | b]? (Linear Algebra)












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I got a question in my textbook where I am supposed to find if the linear system Ax=b is consistent. Then we are given some information. I do think I know how to solve this kind of problem but they use this notation Rank$[A | $b$]$ where it is some kind of number. What does this notation mean?










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    I got a question in my textbook where I am supposed to find if the linear system Ax=b is consistent. Then we are given some information. I do think I know how to solve this kind of problem but they use this notation Rank$[A | $b$]$ where it is some kind of number. What does this notation mean?










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      $begingroup$


      I got a question in my textbook where I am supposed to find if the linear system Ax=b is consistent. Then we are given some information. I do think I know how to solve this kind of problem but they use this notation Rank$[A | $b$]$ where it is some kind of number. What does this notation mean?










      share|cite|improve this question









      $endgroup$




      I got a question in my textbook where I am supposed to find if the linear system Ax=b is consistent. Then we are given some information. I do think I know how to solve this kind of problem but they use this notation Rank$[A | $b$]$ where it is some kind of number. What does this notation mean?







      linear-algebra matrix-rank






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      asked Dec 18 '18 at 14:11









      J. DoeJ. Doe

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          If the system of equations is written in matrix form, $Amathbf{x}=mathbf{b}$, then $A$ is the coefficient matrix and $[A|mathbf{b}]$ is the so called augmentend matrix: the matrix formed by adding a column to $A$, consisting of the constants $mathbf{b}$ from the system of equations (the right-hand side). You can check the Wikipedia page for some examples.






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            I'm guessing that $[A|b]$ refers to the augmented matrix formed by augmenting the column vector $b$ onto the matrix $A$. That is, it's a matrix with one extra column: $b$.



            Note that the equation $Ax = b$ has a solution if and only if $b$ is in the columnspace of $A$ and $operatorname{Rank} [A | b] = operatorname{Rank} A$. Otherwise, $operatorname{Rank} [A | b] = operatorname{Rank} A + 1$.






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              2 Answers
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              2 Answers
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              $begingroup$

              If the system of equations is written in matrix form, $Amathbf{x}=mathbf{b}$, then $A$ is the coefficient matrix and $[A|mathbf{b}]$ is the so called augmentend matrix: the matrix formed by adding a column to $A$, consisting of the constants $mathbf{b}$ from the system of equations (the right-hand side). You can check the Wikipedia page for some examples.






              share|cite|improve this answer









              $endgroup$


















                2












                $begingroup$

                If the system of equations is written in matrix form, $Amathbf{x}=mathbf{b}$, then $A$ is the coefficient matrix and $[A|mathbf{b}]$ is the so called augmentend matrix: the matrix formed by adding a column to $A$, consisting of the constants $mathbf{b}$ from the system of equations (the right-hand side). You can check the Wikipedia page for some examples.






                share|cite|improve this answer









                $endgroup$
















                  2












                  2








                  2





                  $begingroup$

                  If the system of equations is written in matrix form, $Amathbf{x}=mathbf{b}$, then $A$ is the coefficient matrix and $[A|mathbf{b}]$ is the so called augmentend matrix: the matrix formed by adding a column to $A$, consisting of the constants $mathbf{b}$ from the system of equations (the right-hand side). You can check the Wikipedia page for some examples.






                  share|cite|improve this answer









                  $endgroup$



                  If the system of equations is written in matrix form, $Amathbf{x}=mathbf{b}$, then $A$ is the coefficient matrix and $[A|mathbf{b}]$ is the so called augmentend matrix: the matrix formed by adding a column to $A$, consisting of the constants $mathbf{b}$ from the system of equations (the right-hand side). You can check the Wikipedia page for some examples.







                  share|cite|improve this answer












                  share|cite|improve this answer



                  share|cite|improve this answer










                  answered Dec 18 '18 at 14:15









                  StackTDStackTD

                  22.6k2049




                  22.6k2049























                      1












                      $begingroup$

                      I'm guessing that $[A|b]$ refers to the augmented matrix formed by augmenting the column vector $b$ onto the matrix $A$. That is, it's a matrix with one extra column: $b$.



                      Note that the equation $Ax = b$ has a solution if and only if $b$ is in the columnspace of $A$ and $operatorname{Rank} [A | b] = operatorname{Rank} A$. Otherwise, $operatorname{Rank} [A | b] = operatorname{Rank} A + 1$.






                      share|cite|improve this answer









                      $endgroup$


















                        1












                        $begingroup$

                        I'm guessing that $[A|b]$ refers to the augmented matrix formed by augmenting the column vector $b$ onto the matrix $A$. That is, it's a matrix with one extra column: $b$.



                        Note that the equation $Ax = b$ has a solution if and only if $b$ is in the columnspace of $A$ and $operatorname{Rank} [A | b] = operatorname{Rank} A$. Otherwise, $operatorname{Rank} [A | b] = operatorname{Rank} A + 1$.






                        share|cite|improve this answer









                        $endgroup$
















                          1












                          1








                          1





                          $begingroup$

                          I'm guessing that $[A|b]$ refers to the augmented matrix formed by augmenting the column vector $b$ onto the matrix $A$. That is, it's a matrix with one extra column: $b$.



                          Note that the equation $Ax = b$ has a solution if and only if $b$ is in the columnspace of $A$ and $operatorname{Rank} [A | b] = operatorname{Rank} A$. Otherwise, $operatorname{Rank} [A | b] = operatorname{Rank} A + 1$.






                          share|cite|improve this answer









                          $endgroup$



                          I'm guessing that $[A|b]$ refers to the augmented matrix formed by augmenting the column vector $b$ onto the matrix $A$. That is, it's a matrix with one extra column: $b$.



                          Note that the equation $Ax = b$ has a solution if and only if $b$ is in the columnspace of $A$ and $operatorname{Rank} [A | b] = operatorname{Rank} A$. Otherwise, $operatorname{Rank} [A | b] = operatorname{Rank} A + 1$.







                          share|cite|improve this answer












                          share|cite|improve this answer



                          share|cite|improve this answer










                          answered Dec 18 '18 at 14:15









                          Theo BenditTheo Bendit

                          17.3k12149




                          17.3k12149






























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