# Need help : Rank of Determinant

### Need help : Rank of Determinant

Please , I need help for the attached question . Thanks
Attachments
matrix.png (7.57 KiB) Viewed 222 times
Mahmoud Ibrahim

Posts: 9
Joined: Mon May 21, 2018 4:42 am
Reputation: 1

### Re: Need help : Rank of Determinant

If rank of A is 2 , then the determinant of A must be equal to 0 ( det A = 0 ) Det A = 2.0.(-1) + 4.3.k+1.1.2 - 2.0.3 - 1.(-1).k-2.4.1=12k+2 - 8 +k =13k - 6
$$detA=0\Leftrightarrow k = \frac{6}{13}$$

nathi123

Posts: 17
Joined: Sun Sep 17, 2017 1:56 pm
Reputation: 16

### Re: Need help : Rank of Determinant

Thanks very much.

Mahmoud Ibrahim

Posts: 9
Joined: Mon May 21, 2018 4:42 am
Reputation: 1

### Re: Need help : Rank of Determinant

Mat_Rank.png (7.28 KiB) Viewed 135 times
Please. In this question, det(A)$$\ne$$ zero
And any minor determinant containing K not equal zero.
How can I find the real value of K ?
Thank you very much.
Guest

### Re: Need help : Rank of Determinant

Note:
the second row = the first + 1.
As : the first column , 0 = -1 + 1 and in the third column 2 = 1 + 1
Is this means that in the second column K = 3 + 1 , then k = 4 ???
Is this answer correct ? If so , why the question said that R(A) = 3 ?.
In this case what we get from R(A) = 3 ??
Thank you again.
Guest