disable nvidia 840m

After several days of trying I gave up.:banghead: So I have an Acer E5-572G-38HC laptop. Specs : Cpu:Core i3-4000M 2.4 Ghz IGPU:HD4600 (working after installing patched kext and framework) Dedicated GPU: NVIDIA 840M (I want to disable it for power saving) RAM :4GB Installed Yosemite 10.10.2...