Since the Athlon 750k is not on HP's official supported APU (or CPU) list, it may not work with your PC. Yes, the Athlon 750k is socket FM2. Yes, it will physically fit in the motherboard's FM2 socket. But if that processor cannot be identified by the BIOS it will likely not even boot up or it will boot up, but since the BIOS may not be able to specifically identify the processor, it may only run at reduced speeds which more or less defeats the purpose of the upgrade.
You can attempt to install the Athlon 750k, but you run the risk of having to return the CPU if it does not work properly. That generally involves paying to ship it back to wherever you bought it and paying a 15% restocking fee.