Most points given on correct mathematical argumentation

a) (C, 20) Given f(x)=4-x 2-2x 4 and g(x)=2x 5 +18x+1 In what interval does x belong so that f'(x)/g'(x)>0.

b) (C, 20) Find the angle that the tangent of y=(x2+4x-17)1/3, at x=2.5 forms with the positive part of the x axis. Also find the equation of that tangent.

c) (C, 40) Given the function y=x 3 -3ax 2 +3a 2x-3x-l. Find a so that ymax+ymin=0