39. f(e)=2 cos 0+ cos 0, 002 40. S(x)=x-sin x, 0x4 41. Suppose the derivative of a function fis f'(x) = (x + 1)(x-3)5(x-6). On what interval is f increasing? 42. Use the methods of this section to sketch the curve y=x-3ax+ 2a, where a is a positive constant. What do the members of this family of curves have in common? How do they differ from each other?