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How to disable the main GPU of a laptop using Manjaro linux GRUB command line?

I have a sony Vaio VPCEB46FA and the ATI GPU got fried because of overload (it doesnt work anymore) so I wanted to disable it and run on the Intel GPU.
I Have Manjaro OS which is an Arch linux based OS and it doesnt allow me to access the GUI so I need to do this on the GRUB command line.

Thank you in advance.