# Thread: Just started doing maths again last week, stuck on factorising problem

1. ## Just started doing maths again last week, stuck on factorising problem

Factorise x² + 2x + 1 - y²

After trying this for ages, I looked at the answer and its
(x + 1 - y)(x + 1 + y)
but I still can't get to that point by myself, can anyone help please
Thanks

2. Hello OllieRowntree

Welcome to Math Help Forum!
Originally Posted by OllieRowntree
Factorise x² + 2x + 1 - y²

After trying this for ages, I looked at the answer and its
(x + 1 - y)(x + 1 + y)
but I still can't get to that point by myself, can anyone help please
Thanks
Two facts that you need to learn:

• $x^2+2x+1 = (x+1)^2$

• $a^2-b^2 = (a+b)(a-b)$

If you know these, you can use them very easily to solve your problem:

$x^2+2x+1-y^2 = (x+1)^2-y^2$

Can you now apply the second of the two facts to finish the job?