I have Asus N551ZU with integrated R7 1gb and discrete R9 4gb
Every game such as rainbow six only detect the r7 with 1gb VRAM
Can someone solve this, i already try everything from set it to high performance until update everything, and no one can solve this (especially my N551ZU)
The newer laptops (basically everything made in the last 7 years) with hybrid graphics (integrated + dedicated GPU) work by having the integrated GPU always drive the screen. The dedicated GPU acts as a coprocessor. When the game finishes drawing a frame on the dGPU, the frame gets sent to the integrated GPU for display.
This process is highly dependent on having the right video drivers. On my old laptop with Nvidia graphics, for about a year the drivers that Windows 10 Update insisted on installing did not work. I had to download drivers from my laptop manufacturer's website, turn off Windows Update, and install the vendor-provided drivers (for both the integrated and dedicated GPUs). If I turned Windows Update back on, it would overwrite the working drivers with broken ones. They drivers Win 10 Update installed finally began working late last year.
I don't know have a laptop with AMD graphics, but I imagine a similar situation could happen there. It did happen when I was setting up a laptop with AMD graphics 4 years ago. The Windows Update-provided drivers didn't work, while the manufacturer-provided drivers did. At the time Windows 8 (and later 10) had an option to decline device driver updates. Microsoft mysteriously removed that option in a later Win 10 build, which caused the problems with my Nvidia laptop. They didn't put the option back until early 2018 (you have to go into the driver properties, and revert it to remove the Update-provided driver).
So try downloading the video drivers (for both GPUs) from the Asus website. Turn off network connectivity (so Windows Update doesn't immediately overwrite them), and install the two drivers. See if it works with those drivers.