Concrete cutting versus replacing the whole slab
If one panel is cracked or sunken and the rest sits flat and solid, cutting out that piece and pouring just the gap is usually the better use of your money. When the whole slab is settling, the trouble is usually the subgrade, the dirt and gravel it sits on, and a patch would sit on that same bad ground. I'd rather tell you that up front than sell you a patch that sinks along with the rest.

