suppose that $V$ is a finite dimensional and $U$ is a subspace of $V$ such that $dim U = dim V$. Prove $U =...











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I get stuck in this exercise. Can some one give me a hand? It is from Linear Algebra Done Right, from Sheldon Axler.










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    Consider a basis of $U$. Perhaps it is also a basis of $V$.
    – ajotatxe
    yesterday










  • What do you know about the concept of "dimension" in linear algebra? List a couple of properties, and see if you can't find one which you can use as leverage to your advantage.
    – Arthur
    yesterday












  • Ajotaxe, i did it, in my proof the basis of V must be equal to the basis of U, to V=U. But i really dont know if is what the exercice propose. I assume that existe v belonging to V that must belong to U as well. And i open up everything with a linear combination. then i did v-v, and again open up as a linear combination. I got b1.u1 + ... + bn.un = a1v1 + ... + anvn. But i really think this is wrong, or not a good proof.
    – Jeremias Junior
    yesterday










  • Arthur, i will try again. And see if i miss something.
    – Jeremias Junior
    yesterday










  • @ajotatxe if U is a subspace of V and in this case dim U = dim V, then the basis of U must be the same of V, by definition ?
    – Jeremias Junior
    yesterday

















up vote
0
down vote

favorite












I get stuck in this exercise. Can some one give me a hand? It is from Linear Algebra Done Right, from Sheldon Axler.










share|cite|improve this question









New contributor




Jeremias Junior is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
















  • 1




    Consider a basis of $U$. Perhaps it is also a basis of $V$.
    – ajotatxe
    yesterday










  • What do you know about the concept of "dimension" in linear algebra? List a couple of properties, and see if you can't find one which you can use as leverage to your advantage.
    – Arthur
    yesterday












  • Ajotaxe, i did it, in my proof the basis of V must be equal to the basis of U, to V=U. But i really dont know if is what the exercice propose. I assume that existe v belonging to V that must belong to U as well. And i open up everything with a linear combination. then i did v-v, and again open up as a linear combination. I got b1.u1 + ... + bn.un = a1v1 + ... + anvn. But i really think this is wrong, or not a good proof.
    – Jeremias Junior
    yesterday










  • Arthur, i will try again. And see if i miss something.
    – Jeremias Junior
    yesterday










  • @ajotatxe if U is a subspace of V and in this case dim U = dim V, then the basis of U must be the same of V, by definition ?
    – Jeremias Junior
    yesterday















up vote
0
down vote

favorite









up vote
0
down vote

favorite











I get stuck in this exercise. Can some one give me a hand? It is from Linear Algebra Done Right, from Sheldon Axler.










share|cite|improve this question









New contributor




Jeremias Junior is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











I get stuck in this exercise. Can some one give me a hand? It is from Linear Algebra Done Right, from Sheldon Axler.







linear-algebra






share|cite|improve this question









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Jeremias Junior is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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edited yesterday









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Jeremias Junior is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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  • 1




    Consider a basis of $U$. Perhaps it is also a basis of $V$.
    – ajotatxe
    yesterday










  • What do you know about the concept of "dimension" in linear algebra? List a couple of properties, and see if you can't find one which you can use as leverage to your advantage.
    – Arthur
    yesterday












  • Ajotaxe, i did it, in my proof the basis of V must be equal to the basis of U, to V=U. But i really dont know if is what the exercice propose. I assume that existe v belonging to V that must belong to U as well. And i open up everything with a linear combination. then i did v-v, and again open up as a linear combination. I got b1.u1 + ... + bn.un = a1v1 + ... + anvn. But i really think this is wrong, or not a good proof.
    – Jeremias Junior
    yesterday










  • Arthur, i will try again. And see if i miss something.
    – Jeremias Junior
    yesterday










  • @ajotatxe if U is a subspace of V and in this case dim U = dim V, then the basis of U must be the same of V, by definition ?
    – Jeremias Junior
    yesterday
















  • 1




    Consider a basis of $U$. Perhaps it is also a basis of $V$.
    – ajotatxe
    yesterday










  • What do you know about the concept of "dimension" in linear algebra? List a couple of properties, and see if you can't find one which you can use as leverage to your advantage.
    – Arthur
    yesterday












  • Ajotaxe, i did it, in my proof the basis of V must be equal to the basis of U, to V=U. But i really dont know if is what the exercice propose. I assume that existe v belonging to V that must belong to U as well. And i open up everything with a linear combination. then i did v-v, and again open up as a linear combination. I got b1.u1 + ... + bn.un = a1v1 + ... + anvn. But i really think this is wrong, or not a good proof.
    – Jeremias Junior
    yesterday










  • Arthur, i will try again. And see if i miss something.
    – Jeremias Junior
    yesterday










  • @ajotatxe if U is a subspace of V and in this case dim U = dim V, then the basis of U must be the same of V, by definition ?
    – Jeremias Junior
    yesterday










1




1




Consider a basis of $U$. Perhaps it is also a basis of $V$.
– ajotatxe
yesterday




Consider a basis of $U$. Perhaps it is also a basis of $V$.
– ajotatxe
yesterday












What do you know about the concept of "dimension" in linear algebra? List a couple of properties, and see if you can't find one which you can use as leverage to your advantage.
– Arthur
yesterday






What do you know about the concept of "dimension" in linear algebra? List a couple of properties, and see if you can't find one which you can use as leverage to your advantage.
– Arthur
yesterday














Ajotaxe, i did it, in my proof the basis of V must be equal to the basis of U, to V=U. But i really dont know if is what the exercice propose. I assume that existe v belonging to V that must belong to U as well. And i open up everything with a linear combination. then i did v-v, and again open up as a linear combination. I got b1.u1 + ... + bn.un = a1v1 + ... + anvn. But i really think this is wrong, or not a good proof.
– Jeremias Junior
yesterday




Ajotaxe, i did it, in my proof the basis of V must be equal to the basis of U, to V=U. But i really dont know if is what the exercice propose. I assume that existe v belonging to V that must belong to U as well. And i open up everything with a linear combination. then i did v-v, and again open up as a linear combination. I got b1.u1 + ... + bn.un = a1v1 + ... + anvn. But i really think this is wrong, or not a good proof.
– Jeremias Junior
yesterday












Arthur, i will try again. And see if i miss something.
– Jeremias Junior
yesterday




Arthur, i will try again. And see if i miss something.
– Jeremias Junior
yesterday












@ajotatxe if U is a subspace of V and in this case dim U = dim V, then the basis of U must be the same of V, by definition ?
– Jeremias Junior
yesterday






@ajotatxe if U is a subspace of V and in this case dim U = dim V, then the basis of U must be the same of V, by definition ?
– Jeremias Junior
yesterday

















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