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Factor x^3 + 2x^2 + 3x + 6

Step by step, with the reason for every step · Factor by grouping · Algebra 1

Step by step

The question

Question: factor x³ + 2x² + 3x + 6.

There are four terms.

So we factor them in pairs.

This is called grouping.

x3 + 2x2 + 3x + 6

1 Group in pairs

We put the first two together, and the last two together.

= (x3 + 2x2) + (3x + 6)

From the first pair we take out x².

From the second pair we take out 3.

Both leave the same bracket, x + 2.

(x3 + 2x2) = x2(x + 2)
(3x + 6) = 3(x + 2)

Now both parts have x + 2 in them.

= x2(x + 2) + 3(x + 2)

Careful!

This is not the answer yet.

It is still two parts added.

Factored means one thing times another.

Careful: not done yet: still a + between two parts

2 Same bracket out

x + 2 is in both parts, so we take it out once.

What is left, x² + 3, goes in the other bracket.

ab + cb = b(a + c)

So we get (x + 2)(x² + 3).

= (x + 2)(x2 + 3)

3 Check

Let's check: we multiply it back out.

Each part of the first bracket times each part of the second.

Check: (x + 2)(x2 + 3) = x3 + 3x + 2x2 + 6
= x3 + 2x2 + 3x + 6

We get x³ + 2x² + 3x + 6 again.

So the answer is right!

Let's look back.

First: group in pairs.

Then: same bracket out.

Last: check.

Answer
= (x + 2)(x2 + 3)

Your turn

Try this one yourself, then check:

Factor x3 + x2 + 6x + 6
Show the answer
(x + 1)(x2 + 6)

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