First time poster here!

I am reading through some calculus proofs on derivatives and I'm a little rusty on some of my algebra. Would someone mind helping me figure out the steps to go from #1 to #2?

#1

#2

I would like to politely request a step by step answer if you wouldn't mind because i don't remember much about this from Algebra. You will not insult my intelligence. Thanks in advance for your help.

-db