Step by step
The question
Question: simplify (x + 1)(x − 5)/(x² − 25).
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: (x + 1)(x − 5).
It is already factored: (x + 1)(x − 5) means (x + 1) times (x − 5).
We just read the factors.
So the top is (x + 1)(x − 5).
2 Factor the bottom
We look at the bottom: x² − 25.
x² − 25 is x² minus 5 squared.
A square minus a square is the plus bracket times the minus bracket.
So the bottom is (x + 5)(x − 5).
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 + 1)(x − 5)/(x + 5)(x − 5).
(x − 5)/(x − 5) is 1.
Cross them out.
4 Write what is left
What is left is (x + 1)/(x + 5).
One more thing: the bottom of the question can't be 0.
So x can't be −5 or 5.
5 Check
Let's check with a number: x = 2.
First in the question.
We get 3/7.
Now in our answer.
We get 3/7 too.
Both are 3/7.
So (x + 1)/(x + 5) 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.