how do I "un-partition" my MACINTOSH HD into one big hard drive?

So I was derping around on my computer (it has a 250 gigabyte hard drive) and thought,"hmm I wonder what happens if I partition off 75 gigs of this". believe it or not, it partitioned off 75 gigabytes on my hard drive, so what's the problem? well I have no idea how to make it one big single 250 gigabyte partition again. I tried everything, I did the minus on the partition, I did the slide, I repaired with disk utility, same thing with disk utility from the restart CMD+R, and spent hours on the internet looking for a solution. Is there anyone who can help me here?