# How do you find the adjoint of a 3x3 matrix? can u explain example?

1. Oct 15, 2005

### mr_coffee

2. Oct 15, 2005

### GDogg

To find the adjoint of a A:

$$adj(A)_{ij} = (-1)^{i+j} det[A(j|i)]$$

That means that the entry in the row $$i$$ and column $$j$$ of $$adj(A)$$ is obtained by deleting the column $$j$$ and the row $$i$$ of A and then taking the determinant of that and multipliying by $$(-1)^{i+j}$$

For instance if u have a 3x3 matrix:
http://en.wikipedia.org/math/e36e0138b126ebbcf8fe80cd4f58f3aa.png