a non-trivial number of 15-in Dual Graphics computers suffered from the failure of the discrete graphics chip. If you are NOT using an external display, you may be able to use a hobbyist hack to disable the Discrete graphics processor and continue with only the Integrated graphics processor. If you want to edit Videos or use external display, these hacks will not do anything good for you.
The easiest one to install requires that you boot into single-user mode: Hold command + S at startup. if you get to a black terminal screen with white letters, there is some hope you can apply the patches required.
This hack is not for normal use, you may hurt yourself or you computer, and novice users should not even consider it.