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kingwinner
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1) True or False? If true, prove it. If false, prove that it is false or give a counterexample.
1a) If A is m x n, then A and (A^T)(A) have the same rank.
1b) Let A be m x n and X E R^n. If X E null [(A^T)(A)], then AX is in both col(A) and null(A^T).
[I believe it's true that AX is in null(A^T), but I am totally unsure whether AX is in col(A) or not!?]
1c) If U and W are subspaces of a vector space V, then the set of vectors that belong to either U or W is a subspace of V.
2) Prove that if A is an m x n matrix, then null(A)=[col(A^T)]^|
[Using dimension theorem, I proved that their dimensions are equal...but I have no idea how to prove that they ARE equal...]
These are also the past exams questions that I am having terrible trouble with. Can someone give me some advice/hints? For 1b) and 2), I am partially done, but how 1a)c) I have no clue...
Any help/hints is greatly appreciated!
1a) If A is m x n, then A and (A^T)(A) have the same rank.
1b) Let A be m x n and X E R^n. If X E null [(A^T)(A)], then AX is in both col(A) and null(A^T).
[I believe it's true that AX is in null(A^T), but I am totally unsure whether AX is in col(A) or not!?]
1c) If U and W are subspaces of a vector space V, then the set of vectors that belong to either U or W is a subspace of V.
2) Prove that if A is an m x n matrix, then null(A)=[col(A^T)]^|
[Using dimension theorem, I proved that their dimensions are equal...but I have no idea how to prove that they ARE equal...]
These are also the past exams questions that I am having terrible trouble with. Can someone give me some advice/hints? For 1b) and 2), I am partially done, but how 1a)c) I have no clue...
Any help/hints is greatly appreciated!