Cannot uninstall SPECIFIC preinstalled Metro apps W8.1

Hello, i have a problem regarding uninstalling some Metro apps that came preinstalled with Windows 8.1. Those apps are called Camera, Photos and OneDrive. I cannot uninstall them because none of the methods posted in Tutorials works: those apps doesn't have an "Uninstall" option like the others and it isn't possible via PowerShell, because i get an error. Does this means that isn't possible to uninstall them or it is another method that i don't know yet ? Please tell me.