15. [12 Points] DETAILS The derivative of a function f(x) at x = a is given by lim x/17+x3 Xe -8 x + 8 Find f(x) and a. we =E a: Submit Answer 16. [-12 Points] DETAILS The derivative of a function f(x) at x = a is given by "m 3'27 +h 3 hao h ' Find f(x) and 3. Submit Answer 17. [-13 Points] DETAILS The position function of a particular particle is given by f(t) = t3 + 2t + 9. Assume that it is defined for t. (a) What is the velocity function of the particle? (b) What is the velocity of the particle when t = 4? (c) What is the speed of the particle when t = 4