Rút gọn biểu thức: 2(sin^6x+cos^6x) - 3(sin^4x+cos^4x)

`2(sin^6x+cos^6x)-3(sin^4x+cos^4x)`

`=2[(sin^2x+cos^2x)(sin^4x-sin^2xcos^2x+cos^4x)]-3(sin^4x+2sin^2xcos^2x+cos^4x-2sin^2xcos^2x)`

`=2(sin^4x+2sin^2xcos^2x+cos^4x-3sin^2xcos^2x)-3[(sin^2x+cos^2x)-2sin^2xcos^2x]`

`=2[(sin^2x+cos^2x)-3sin^2xcos^2x]-3(1-2sin^2xcos^2x)`

`=2(1-3sin^2xcos^2x)-3+6sin^2xcos^2x)`

`=2-6sin^2xcos^2x-3+6sin^2xcos^2x`

`=-1`