Both questions plz

5. The position of a particle moving in a straight line is given by s(t) = x3 - 4x + 1, where s is measured in meters and t is measured in seconds. a.) At what time t is the velocity of the particle equal to 8 m/s? b.) What is the acceleration of the particle at the time found in part a? Math 400 Name 6. A newly discovered radioactive substance is found to have a half-life of 15 days. How long will it take a 100g sample of this substance to decay to a mass of 30g