6. (12 points) Find the limit of the following: a) lim X - 6 x-6 x(x2-36) 6a) b) lim cosx = it cot x 6b) 7. (7 points) Using the 8 - & definition, prove that lim (3x + 7) = 4. x - - 1 8. (8 points) If the position of an object is s(t) = -5t3 + 2t2 - 8t meters in t seconds; a) Determine the velocity of the object at t = 1 seconds. 8a) b) Find the acceleration of the object at t = 1 seconds. 8b)