Det [6, 3; 2, 5]

Step by step

The question

Question: find the determinant of this matrix.

The determinant is one number we get from a square matrix.

We write the matrix between two straight lines, and call it D.

1 Multiply the diagonals

So D = 6 × 5 − 2 × 3.

Careful!

Always down minus up.

Up minus down gives the wrong sign.

2 Down minus up

6 times 5 is 30.

2 times 3 is 6.

30 minus 6 is 24.

So D = 24.

3 Check

Let's check the taking away by adding back: 24 + 6 = 30, the down product.

So D = 24 is right!

Let's look back.

First: multiply the diagonals.

Then: down minus up.

Last: check.