[xubuntu] Problems with Xubuntu 16.04 and Intel/Nvidia graphic cards

Hi everyone,
I have a notebook Santech t67 with the following features : CPU intel core i7-6700HQ, 16 Gb RAM, Nvidia GeForce GTX 970M + intel integrated card. I installed Xubuntu 16.04 in dual boot with Windows 10 without problems. I have a problem ( sorry for the repetition ) regarding the management of dedicated Nvidia video card and integrated Intel card. I installed the proprietary Nvidia and Intel drivers and I set the Intel one to improve the autonomy of the pc. The system works perfectly, only when I tu it off or reboot it freezes in a black screen with a white dash in the top left coer, forcing me to force it to close. If I use the Nvidia card this does not happen ( the computer tus off and restarts normally) . Someone has the same problem or know a possible solution?