Step by step
The question
Question: work out 4 times this matrix.
4[1, −2, 3]
A matrix is numbers in rows and columns, inside big brackets.
Each number in a matrix is called an entry.
1 Times every entry
4 in front means: every entry times 4.
We write 4 × in front of each one.
= [4 × 1, 4 × (−2), 4 × 3]
Careful!
Every entry gets times 4, in every row.
Not only the first one.
Careful: every entry × 4, every row
Now we work out each one.
4 times 1 is 4, and so on.
The answer: the row 4, −8, 12.
= [4, −8, 12]
2 Check
Let's check by dividing back: each entry divided by 4.
4 ÷ 4 = 1, −8 ÷ 4 = −2, 12 ÷ 4 = 3
We get the first matrix back.
So the answer is right!
Let's look back.
First: times every entry.
Last: check.
Answer
= [4, −8, 12]