Wednesday 20 March 2013

Important points chapter 3 book 1

Determinant of a diagonal matrix is equal to the product of its main diagonal elements.

No common element is present between two diagonals of a matrix of even order.
A   (n+1)/2 is common element of two diagonals o f a matrix of odd order n.
A2 is always symmetric for A being either symmetric or skew-symmetric.


Non-homogenous system:
1.     A system is said to be consistent if its solution exists otherwise inconsistent.
2.     If |A|=0 then solution does not exists.
3.     If |A|≠ 0 then solution exist.
4.     Solution exists if A is non-singular.
5.     Solution will exist if
a.      Rank of A = rank of Ab
6.     If rank of A = rank of Ab= number of variables
a.      Then solution is unique.
7.     If rank of A = rank of Ab <  number of variables
a.      Then solutions are infinite.

Homogenous system:
1.     Every homogenous system has trivial or zero solution.
2.     For non-trivial solution |A|=0
3.     If |A≠0 then non-trivial solution does not exist.
Note:
In all above cases A is the matrix of co-efficient.

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