6. (12 points) Find the limit of the following: a) lim x-6 X-6 *(x2-36) 6a) b) lim cosx = it cot x 6b) 7. (6 points) Using the 6 -& definition, prove that lim (3x + 7) = 4. *- -1 8. (4 points) If the position of an object is s(t) = -t3 + 6t2 - 9t meters in f seconds; a) Determine the velocity of the object at / = 2 seconds. 8a) b) Find the acceleration of the object at t = 2 seconds