LA240PM200 is not a battery -- it's an AC adapter.  It is compatible with the X15. ga240PE1-00 is also not a battery -- it is another AC adapter.  It is an older model, designed for older Alienware systems.  However, it should also work with the X15.    
I would like to ask if the battery models ga240PE1-00 and LA240PM200 are compatible with the same size. model: alienware x15 gaming laptop
Enquiry of battery compatible