The determinant of 2 by 2
matrix can be worked out almost instantly:
ie
multiply the diagonal numbers together and subtract them.
The determinant of a 3 by 3 matrix is
much more difficult. We have to carry out a process called expanding
along a row or a column, In the example below I will expand along a
row – the top row.
Example:
We label the positions in the matrix
with +1's and -1's:
For
the first term, 3, cross out the entries in the same row and column
as this 3.
For
the first term, 3, cross out the entries in the same row and column
as this 3.
Our
second term is
Our
third term is
The determinant is
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