If . Write the cofactor of the element a32.
We are given that,
We need to find the cofactor of the element a32.
A cofactor is the number you get when you remove the column and row of a designated element in a matrix, which is just a numerical grid in the form of a rectangle or a square. The cofactor is always preceded by a positive (+) or negative (-) sign, depending whether the element is in a + or - position. It is
Let us recall how to find the cofactor of any element:
If we are given with,
Cofactor of any element, say a11 is found by eliminating first row and first column.
⇒ Cofactor of a11 = a22 × a33 – a23 × a32
The sign of cofactor of a11 is (+).
And, cofactor of any element, say a12 is found by eliminating first row and second column.
⇒ Cofactor of a12 = a21 × a33 – a23 × a31
The sign of cofactor of a12 is (-).
So,
In matrix, .
Element at a32 = 2
We need to find the cofactor of 2 at a32.
And as discussed above, the sign at a32 is (-).
For cofactor of a32, eliminate third row and second column in the matrix.
⇒ Cofactor of a32 = 5 × 1 – 8 × 2
⇒ Cofactor of a32 = 5 – 16
⇒ Cofactor of a32 = -11
Since, the sign of cofactor of a32 is (-), then
Cofactor of a32 = -(-11)
⇒ Cofactor of a32 = 11
Thus, cofactor of a32 is 11.