The other tutor's solution is incorrect:

Factor out  from the two red terms:

(Don't forget that when you factor out a negative, 
the signs change inside the parentheses!)



Factor out  from the two blue terms:



Now I'll do some re-coloring:



Take out the green 



That's it!  You can make it a tiny bit shorter by
reversing the terms in the second factor:



But that is not necessary.  To make the green one
match, you might want to reverse the terms in it too:



and then leave the whole thing black, like this:



But it would be OK just to leave it like we had it above
without the coloring:



Edwin