Đáp án+Giải thích các bước giải:

`M = cos^6x + 2sin^6x + sin^4xcos^2x + 4sin^2xcos^2x - sin^2x`

`M = sin^4x( sin^2x + cos^2x ) + ( cos^6x + sin^6x ) + 4sin^2xcos^2x - sin^2x`

`M = sin^4x + ( cos^2x + sin^2x )( cos^4x - cos^2xsin^2x + sin^4x) + 4sin^2xcos^2x - sin^2x`

`M = sin^2x( sin^2x - 1 ) + cos^4x - cos^2xsin^2x + sin^4x + 4sin^2xcos^2x`

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

`M = sin^4x + 2sin^2xcos^2x + cos^4x`

`M = ( sin^2x + cos^2x )^2`

`M = 1^2 = 1`