Find a_13 in [2, 0, 6; 1, 4, -5]

Step by step

The question

Question: in A, find a₁⁣₃.

A matrix is numbers in rows and columns, inside big brackets.

Each number in a matrix is called an entry.

a₁⁣₃ names one entry.

The small numbers say where it is: first the row, 1.

Then the column, 3.

1 Find row 1

Rows go across.

We count down to row 1.

Row 1 is 2, 0, 6.

2 Find column 3

Columns go down.

We count across to column 3.

Column 3 is 6, −5.

Row 1 and column 3 meet at 6.

So a₁⁣₃ = 6.

Careful!

The first small number is always the row, the second is the column.

3 Check

Let's check the other way.

We go down column 3, and stop at row 1.

We land on 6 again.

So it is right!

Let's look back.

First: find row 1.

Then: find column 3.

Last: check.