a)y' = -sin(1/7x + 4) • (1/7x+4)' = -1/7sin(1/7x + 4)

b)y' = 4(sin4x - 3)³ • (sin4x - 3)' = 4(sin4x -3)³ • 4cos4x = 16cos4x(sin4x - 3)³