Before you read this, say "maths is interesting!". Mental trick....
Now you may start.
In matrices, there is an important basic term residing in it.
It is the term called "minor" and is obtained through the determinant of the matrix.
For 2nd order matrix (or determinant), there will be 4 minors since there are 4 elements within the determinant.
For 3rd order form, there will inevitably, be 9 minors.
To have an idea what "order of matrix" is about, go to this link here.
How to compute this minor?
The method is simple, right?
It involves the correct cancellation of the appropriate row and column.
The leftover elements will be used to determine the value.
To enhance understanding, let's do another example.Find the minor of element 2.
The leftover is the elements
The determinant value of the leftover is then (4)(9) - (7)(6) = 36 - 42 = -6.
This is the minor for element "2".
Common mistake made:
The minor is always taken as the actual element in question.
Example of mistakes:
To find the minor of element "2" in the above determinant
==> Wrong answer = "2", the original element used to get the leftover after cancellation.
To find the minor of element "1" in the above determinant
==> Wrong answer = "1", the original element used to get the leftover after cancellation.
Minor and Co-factor are closely related. They are needed to compute Adjoint and Inverse matrix.
You have to master these concepts to be able to handle matrices.
Tough, right? If your answer is YES, you are wrong!
Look and review the above methods again, and you will be sure that they are simply +, _, x only.
Isn't this what you have been learning since lower elementary?