Just a quick keyword question for you all.

I have found a keyword phrase I like, and think I can rank for, but then by adding a single word at the end of that phrase, the competition greatly decreased. So my question is if I target the same phrase with one more word, will I also be targeting the phrase minus that extra word?

Example: ummm

How to grow hair (original)

How to grow hair fast (with added word)

So, being that the first four words are the same, will I be in a way targeting the shorter phrase, because it is part of the longer phrase? Thank you very much in advanced.