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Q18E
Expert-verifiedIn Exercise 18, A is an \(m \times n\) matrix. Mark each statement True or False. Justify each answer.
18. a. If B is any echelon form of A, then the pivot columns of B form a basis for the column space of A.
b. Row operations preserve the linear dependence relations among the rows of A.
c. The dimension of the null space of A is the number of columns of A that are not pivot columns.
d. The row space of \({A^T}\) is the same as the column space of A.
e. If A and B are row equivalent, then their row spaces are the same.
(a)
Note that the pivot columns of matrix A only form a basis for Col A.
Hence, the given statement is false.
(b)
The row operations may change the linear dependence relations among the rows of a matrix.
Hence, the given statement is false.
(c)
The sum of the pivot columns and non-pivot columns of A equals the number of columns of A. The number of pivot columns of A is the rank of A.
By the rank theorem, the number of non-pivot columns of A is the dimension of the null space of A.
Hence, the given statement is true.
(d)
The rows of \({A^T}\) are identified with the columns of \({\left( {{A^T}} \right)^T}\), i.e., A. So, you can write \({\rm{Row }}{A^T}\) in place of Col A.
Hence, the given statement is true.
(e)
By Theorem 13, if matrices A and B are equivalent, then their row spaces are the same.
Hence, the given statement is true.
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