Step by step
The question
Question: simplify (x² − 4)/(x² + 4x + 4).
A fraction with x in it is called a rational expression.
We make it simpler like a number fraction.
6/9: both have a 3 in them.
3/3 is 1, so 2/3 is left.
We do the same with brackets.
1 Factor the top
We look at the top: x² − 4.
x² − 4 is x² minus 2 squared.
A square minus a square is the plus bracket times the minus bracket.
So the top is (x + 2)(x − 2).
2 Factor the bottom
We look at the bottom: x² + 4x + 4.
For x² + 4x + 4, we need two numbers.
They multiply to 4, and they add to 4.
They multiply to a plus number, so the two numbers have the same sign.
They add to a plus number, so both are plus.
We list the pairs that make 4, smallest first.
We add each pair.
We need 4.
2 and 2 give 4.
Yes!
So the bottom is (x + 2)(x + 2).
3 Cross out the same
Careful!
We cross out only a whole bracket, or a whole x, that multiplies everything.
Never one part of a bracket.
Now we write the fraction with the factors: (x + 2)(x − 2)/(x + 2)(x + 2).
(x + 2)/(x + 2) is 1.
Cross them out.
4 Write what is left
What is left is (x − 2)/(x + 2).
One more thing: the bottom of the question can't be 0.
So x can't be −2.
5 Check
Let's check with a number: x = 1.
First in the question.
We get −1/3.
Now in our answer.
We get −1/3 too.
Both are −1/3.
So (x − 2)/(x + 2) is right!
Let's look back.
First: factor the top.
Then: factor the bottom.
Then: cross out the same.
Then: write what is left.
Last: check.