y = 2x cos(3x) + (3x2-4) sin(3x)
dy/dx = (2x x -sin(3x) x 3) + (2 x cos(3x)) + (6x sin(3x)) + ((3x2-4) cos(3x) x 3)
dy/dx = -6x sin(3x) + 2 cos (3x) + 6x sin(3x) + (9x2-12) cos(3x)
dy/dx = (9x2-12 + 2) cos (3x) = (9x2-10) cos (3x)
m = 9n = -10