We are given the following expression:
We will associate the terms that have common factors, like this:
Now we take the common factor for each of the parenthesis:
Since each parenthesis has a common factor but with inverted signs, we will take -1 as a common factor in the second parenthesis, we get:
Now we can take "y-r" as a common factor for the entire expression:
And thus we have factored the expression.