Simplify 3i × 4i

Step by step

The question

Question: work out 3i × 4i.

No real number times itself is negative.

So we use a new number: i, the square root of minus 1.

So i squared is minus 1.

1 Multiply each part

3i times 4i is 12i².

2 Change i² to −1

i squared is minus 1.

So 12i² becomes −12.

Now we have −12.

So the answer is −12.

3 Check

Let's check: multiply the other way round, 4i × 3i.

Each part times each part again, and i² is −1.

We get −12 again.

So the answer is right!

Let's look back.

First: multiply each part.

Then: change i² to −1.

Last: check.