Late 2011 MacBook Pro Cannot format HDD

I have a Late 2011 MacBook Pro with 750GB HDD. I was running Yosemite 10.10.2. I had about 250GB of partitioned HDD that i wanted to add to my main partition 'Macintosh HD'. It let me remove the second partition but i couldn't do my normal drag and extend the 'Macintosh HD' partition to take full advantage of my HDD space. After hours of searching i plunged into recovery using Disk Utility and Terminal tried to extend the cold source to use the whole HDD. It still wasn't working so using my critical thinking skills i decided i would just use terminal to wipe the whole drive and start fresh just like i can do in Windows. This failed miserably. I can't do anything at this point. Every time i try to do anything it gives me cannot unmount error and when i try to back up from time machine the only thing its see's is a DISK0S1 that's only 210MB. It boots into recovery and that's about it. I would like to just get my MacBook running again and if possible using the full 750GB HDD. Im not sure if thats possible at this point. Also when i try to use Reinstall OS X it only see's DISK0S1.