Sarahisme Posted May 14, 2005 Share Posted May 14, 2005 Hey can i ask if my answers to this question are correct...? a) yes, because f'(x) = 0 at x = 0 b) yes, because there exists a tangent line at x = 0 (because of part a) and the concavity is of a different sign on both sides of x = 0 (i.e. f''(x) is -ve one left and +ve on right) c) no it is not true, because f''(x) = 2 for all real x in the domain d) no, as can been seen in this question Sarah Link to comment Share on other sites More sharing options...
Dave Posted May 14, 2005 Share Posted May 14, 2005 Seems okay, apart from ©. I don't think your second derivative is quite correct. Link to comment Share on other sites More sharing options...
uncool Posted May 14, 2005 Share Posted May 14, 2005 f''(x) jumps from -2 to 2 at 0. d is therefore anwered incorrectly. The answer is that the second derivative does necessarily vanish. -Uncool- Link to comment Share on other sites More sharing options...
Sarahisme Posted May 15, 2005 Author Share Posted May 15, 2005 ok, so so part c should be c) f''(x) is either -2 or 2, so not zero and d) no not necessarily Link to comment Share on other sites More sharing options...
matt grime Posted May 15, 2005 Share Posted May 15, 2005 Well, in c) you ought to say that the function only has a one sided second derivative at x=0, and some people, like me, would point out that therefore f'' doesn't exist at x=0. Link to comment Share on other sites More sharing options...
Sarahisme Posted May 17, 2005 Author Share Posted May 17, 2005 isnt the first derivative only one sided too? (at x = 0) ?? and therefore the first derivative does not exist at x = 0 ?? Link to comment Share on other sites More sharing options...
Sarahisme Posted May 18, 2005 Author Share Posted May 18, 2005 lol, anyone? or am i way off track? Link to comment Share on other sites More sharing options...
Sarahisme Posted May 19, 2005 Author Share Posted May 19, 2005 nevermind, i am going crazy.... Link to comment Share on other sites More sharing options...
Sarahisme Posted May 19, 2005 Author Share Posted May 19, 2005 i've got it now! problem solved Link to comment Share on other sites More sharing options...
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