The following instructions work specifically well when extending a Virtual Machine partition.
Step 1: Extend your image by clicking your images hard drive in VMWARE or Virtual Box and extending to the desired size.
Step 2: Download the gparted.iso and mount it in the Virtual Machine CD ROM disk section.
Step 3: Boot gparted.
Step 4: Create a second primary partition on the newly made unallocated space, format it as hfs+.
Step 5: Apply changes and boot into your Mac Guest Operating System.
Step 6: Go to Terminal
Step 7: See what your partitions are called by typing in df -h.
In my case the partition are: disk1s2 and disk1s3
Step 8: Type the following: sudo diskutil merge Partitions “Journaled HFS+” New disk1s2 disk1s3
You expanded drive is now complete.
By: Isaac C.