find the dimension of the given space?











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let $W_1$ be the real vector space of all $5 times 2$ matrices of such that the sum the sum of the entries in each row is $0 $. let $W_2$be the real vector space of all $5 times 2$ matrices such that the sum of the entries in each column is zero .find the dimension of the space $W _1 cap W_2$



my attempts :$max[0,dim(W_1)+dim(W_2)- 5] le dim(W_1 ∩ W_2) le min[ dim(W_1) ,dim (W_2),]$



so $dim(W_1 ∩ W_2) = 2$



Am i right ?










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  • 1




    You are not. I suppose that You calculate $dim(W_1)$ and $dim(W_2)$ in a wrong way. $dim(W_2)$ is much larger than $2$.
    – Logic_Problem_42
    May 8 at 5:34








  • 1




    I think the answer is 4. A row vector sums to 0 means it must have dimension 4. And since the columns sum to 0 once the first row is fixed the next row is negative of the first row.
    – Piyush Divyanakar
    May 8 at 5:38















up vote
0
down vote

favorite












let $W_1$ be the real vector space of all $5 times 2$ matrices of such that the sum the sum of the entries in each row is $0 $. let $W_2$be the real vector space of all $5 times 2$ matrices such that the sum of the entries in each column is zero .find the dimension of the space $W _1 cap W_2$



my attempts :$max[0,dim(W_1)+dim(W_2)- 5] le dim(W_1 ∩ W_2) le min[ dim(W_1) ,dim (W_2),]$



so $dim(W_1 ∩ W_2) = 2$



Am i right ?










share|cite|improve this question




















  • 1




    You are not. I suppose that You calculate $dim(W_1)$ and $dim(W_2)$ in a wrong way. $dim(W_2)$ is much larger than $2$.
    – Logic_Problem_42
    May 8 at 5:34








  • 1




    I think the answer is 4. A row vector sums to 0 means it must have dimension 4. And since the columns sum to 0 once the first row is fixed the next row is negative of the first row.
    – Piyush Divyanakar
    May 8 at 5:38













up vote
0
down vote

favorite









up vote
0
down vote

favorite











let $W_1$ be the real vector space of all $5 times 2$ matrices of such that the sum the sum of the entries in each row is $0 $. let $W_2$be the real vector space of all $5 times 2$ matrices such that the sum of the entries in each column is zero .find the dimension of the space $W _1 cap W_2$



my attempts :$max[0,dim(W_1)+dim(W_2)- 5] le dim(W_1 ∩ W_2) le min[ dim(W_1) ,dim (W_2),]$



so $dim(W_1 ∩ W_2) = 2$



Am i right ?










share|cite|improve this question















let $W_1$ be the real vector space of all $5 times 2$ matrices of such that the sum the sum of the entries in each row is $0 $. let $W_2$be the real vector space of all $5 times 2$ matrices such that the sum of the entries in each column is zero .find the dimension of the space $W _1 cap W_2$



my attempts :$max[0,dim(W_1)+dim(W_2)- 5] le dim(W_1 ∩ W_2) le min[ dim(W_1) ,dim (W_2),]$



so $dim(W_1 ∩ W_2) = 2$



Am i right ?







linear-algebra






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edited Nov 15 at 16:00

























asked May 8 at 5:30









jasmine

1,331416




1,331416








  • 1




    You are not. I suppose that You calculate $dim(W_1)$ and $dim(W_2)$ in a wrong way. $dim(W_2)$ is much larger than $2$.
    – Logic_Problem_42
    May 8 at 5:34








  • 1




    I think the answer is 4. A row vector sums to 0 means it must have dimension 4. And since the columns sum to 0 once the first row is fixed the next row is negative of the first row.
    – Piyush Divyanakar
    May 8 at 5:38














  • 1




    You are not. I suppose that You calculate $dim(W_1)$ and $dim(W_2)$ in a wrong way. $dim(W_2)$ is much larger than $2$.
    – Logic_Problem_42
    May 8 at 5:34








  • 1




    I think the answer is 4. A row vector sums to 0 means it must have dimension 4. And since the columns sum to 0 once the first row is fixed the next row is negative of the first row.
    – Piyush Divyanakar
    May 8 at 5:38








1




1




You are not. I suppose that You calculate $dim(W_1)$ and $dim(W_2)$ in a wrong way. $dim(W_2)$ is much larger than $2$.
– Logic_Problem_42
May 8 at 5:34






You are not. I suppose that You calculate $dim(W_1)$ and $dim(W_2)$ in a wrong way. $dim(W_2)$ is much larger than $2$.
– Logic_Problem_42
May 8 at 5:34






1




1




I think the answer is 4. A row vector sums to 0 means it must have dimension 4. And since the columns sum to 0 once the first row is fixed the next row is negative of the first row.
– Piyush Divyanakar
May 8 at 5:38




I think the answer is 4. A row vector sums to 0 means it must have dimension 4. And since the columns sum to 0 once the first row is fixed the next row is negative of the first row.
– Piyush Divyanakar
May 8 at 5:38










1 Answer
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Elements of $W_1 cap W_2$ satisfy the condition that the sum of each row and each column is $0$.



Hence the first row completely determines the next row and the first $4$ entries of the first row would determine the $5$ element, hence the dimension is $4$.






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  • thanks Siong THye
    – jasmine
    May 8 at 7:43











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up vote
4
down vote



accepted










Elements of $W_1 cap W_2$ satisfy the condition that the sum of each row and each column is $0$.



Hence the first row completely determines the next row and the first $4$ entries of the first row would determine the $5$ element, hence the dimension is $4$.






share|cite|improve this answer





















  • thanks Siong THye
    – jasmine
    May 8 at 7:43















up vote
4
down vote



accepted










Elements of $W_1 cap W_2$ satisfy the condition that the sum of each row and each column is $0$.



Hence the first row completely determines the next row and the first $4$ entries of the first row would determine the $5$ element, hence the dimension is $4$.






share|cite|improve this answer





















  • thanks Siong THye
    – jasmine
    May 8 at 7:43













up vote
4
down vote



accepted







up vote
4
down vote



accepted






Elements of $W_1 cap W_2$ satisfy the condition that the sum of each row and each column is $0$.



Hence the first row completely determines the next row and the first $4$ entries of the first row would determine the $5$ element, hence the dimension is $4$.






share|cite|improve this answer












Elements of $W_1 cap W_2$ satisfy the condition that the sum of each row and each column is $0$.



Hence the first row completely determines the next row and the first $4$ entries of the first row would determine the $5$ element, hence the dimension is $4$.







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered May 8 at 6:23









Siong Thye Goh

94.3k1462114




94.3k1462114












  • thanks Siong THye
    – jasmine
    May 8 at 7:43


















  • thanks Siong THye
    – jasmine
    May 8 at 7:43
















thanks Siong THye
– jasmine
May 8 at 7:43




thanks Siong THye
– jasmine
May 8 at 7:43


















 

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