If $sum_{i=1}^vu_iotimes v_i =0$ then $v_i=0$ for all $i=1,cdots, n$











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Let $U$, $V$ be $K$-vector spaces. Let $u_1,cdots, u_nin U$ be linear independent vectors and $v_1,cdots, v_nin V$ arbitrary vectors. Show that if $sum_{i=1}^vu_iotimes v_i =0$ then $v_i=0$ for all $i=1,cdots, n$



I can obviously show the converse, but it does not suffice. I tried to find the answer here but I couldn't. It seems simple but I don't know how to begin










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    Should it be $sum_{i=1}^n$ rather than $sum_{i=1}^v$ in the title and text?
    – Semiclassical
    Nov 17 at 18:35















up vote
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down vote

favorite












Let $U$, $V$ be $K$-vector spaces. Let $u_1,cdots, u_nin U$ be linear independent vectors and $v_1,cdots, v_nin V$ arbitrary vectors. Show that if $sum_{i=1}^vu_iotimes v_i =0$ then $v_i=0$ for all $i=1,cdots, n$



I can obviously show the converse, but it does not suffice. I tried to find the answer here but I couldn't. It seems simple but I don't know how to begin










share|cite|improve this question


















  • 1




    Should it be $sum_{i=1}^n$ rather than $sum_{i=1}^v$ in the title and text?
    – Semiclassical
    Nov 17 at 18:35













up vote
0
down vote

favorite









up vote
0
down vote

favorite











Let $U$, $V$ be $K$-vector spaces. Let $u_1,cdots, u_nin U$ be linear independent vectors and $v_1,cdots, v_nin V$ arbitrary vectors. Show that if $sum_{i=1}^vu_iotimes v_i =0$ then $v_i=0$ for all $i=1,cdots, n$



I can obviously show the converse, but it does not suffice. I tried to find the answer here but I couldn't. It seems simple but I don't know how to begin










share|cite|improve this question













Let $U$, $V$ be $K$-vector spaces. Let $u_1,cdots, u_nin U$ be linear independent vectors and $v_1,cdots, v_nin V$ arbitrary vectors. Show that if $sum_{i=1}^vu_iotimes v_i =0$ then $v_i=0$ for all $i=1,cdots, n$



I can obviously show the converse, but it does not suffice. I tried to find the answer here but I couldn't. It seems simple but I don't know how to begin







linear-algebra






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asked Nov 17 at 18:07









Guerlando OCs

6821450




6821450








  • 1




    Should it be $sum_{i=1}^n$ rather than $sum_{i=1}^v$ in the title and text?
    – Semiclassical
    Nov 17 at 18:35














  • 1




    Should it be $sum_{i=1}^n$ rather than $sum_{i=1}^v$ in the title and text?
    – Semiclassical
    Nov 17 at 18:35








1




1




Should it be $sum_{i=1}^n$ rather than $sum_{i=1}^v$ in the title and text?
– Semiclassical
Nov 17 at 18:35




Should it be $sum_{i=1}^n$ rather than $sum_{i=1}^v$ in the title and text?
– Semiclassical
Nov 17 at 18:35










1 Answer
1






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up vote
1
down vote



accepted










Let $w_1, ldots, w_m$ be a basis of $V$. Then $u_i otimes w_j$ is linearly independent in
$U otimes V$. One can write



$$sum_{i=1}^{n} u_i otimes v_i = sum_{i=1}^{n} u_i otimes left( sum_{j=1}^{m}c^i_j w_jright) = sum_{i=1}^{n} sum_{j=1}^{m} c^i_j (u_i otimes w_j) = 0.$$



Clearly, this implies that all $c^i_j = 0$. Thus, $v_i = sum c^i_j w_j = 0$.






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    up vote
    1
    down vote



    accepted










    Let $w_1, ldots, w_m$ be a basis of $V$. Then $u_i otimes w_j$ is linearly independent in
    $U otimes V$. One can write



    $$sum_{i=1}^{n} u_i otimes v_i = sum_{i=1}^{n} u_i otimes left( sum_{j=1}^{m}c^i_j w_jright) = sum_{i=1}^{n} sum_{j=1}^{m} c^i_j (u_i otimes w_j) = 0.$$



    Clearly, this implies that all $c^i_j = 0$. Thus, $v_i = sum c^i_j w_j = 0$.






    share|cite|improve this answer

























      up vote
      1
      down vote



      accepted










      Let $w_1, ldots, w_m$ be a basis of $V$. Then $u_i otimes w_j$ is linearly independent in
      $U otimes V$. One can write



      $$sum_{i=1}^{n} u_i otimes v_i = sum_{i=1}^{n} u_i otimes left( sum_{j=1}^{m}c^i_j w_jright) = sum_{i=1}^{n} sum_{j=1}^{m} c^i_j (u_i otimes w_j) = 0.$$



      Clearly, this implies that all $c^i_j = 0$. Thus, $v_i = sum c^i_j w_j = 0$.






      share|cite|improve this answer























        up vote
        1
        down vote



        accepted







        up vote
        1
        down vote



        accepted






        Let $w_1, ldots, w_m$ be a basis of $V$. Then $u_i otimes w_j$ is linearly independent in
        $U otimes V$. One can write



        $$sum_{i=1}^{n} u_i otimes v_i = sum_{i=1}^{n} u_i otimes left( sum_{j=1}^{m}c^i_j w_jright) = sum_{i=1}^{n} sum_{j=1}^{m} c^i_j (u_i otimes w_j) = 0.$$



        Clearly, this implies that all $c^i_j = 0$. Thus, $v_i = sum c^i_j w_j = 0$.






        share|cite|improve this answer












        Let $w_1, ldots, w_m$ be a basis of $V$. Then $u_i otimes w_j$ is linearly independent in
        $U otimes V$. One can write



        $$sum_{i=1}^{n} u_i otimes v_i = sum_{i=1}^{n} u_i otimes left( sum_{j=1}^{m}c^i_j w_jright) = sum_{i=1}^{n} sum_{j=1}^{m} c^i_j (u_i otimes w_j) = 0.$$



        Clearly, this implies that all $c^i_j = 0$. Thus, $v_i = sum c^i_j w_j = 0$.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Nov 17 at 18:32









        Jeffery Opoku-Mensah

        3,517719




        3,517719






























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