# Find relative extrema

• Nov 10th 2009, 09:03 PM
jzellt
Find relative extrema
First off, does this mean find relative min and max?

y = x^3 - 3x^2 + 3x - 1

Do I find y' , then set it to 0 and solve for x? That is the min

Do I find y'', then set it to 0 and solve for x? That is the max

I don't need anyone to do this...just explain how to go about it please.

Thanks.
• Nov 10th 2009, 09:20 PM
earboth
Quote:

Originally Posted by jzellt
First off, does this mean find relative min and max? <<<<<< Yes

y = x^3 - 3x^2 + 3x - 1

Do I find y' , then set it to 0 and solve for x? That is the min <<<<<<< No. You determine the x-coordinate of the extremum, maximum or minimum.

Do I find y'', then set it to 0 and solve for x? That is the max <<<<<< No. With y'' = 0 you determine the point of inflection. You can distinguish the min and max using the x-coordinates of the extrema as argumant in y''

I don't need anyone to do this...just explain how to go about it please.

Thanks.

...
• Nov 10th 2009, 09:28 PM
jzellt
So, I guess I'm still a bit confused. How should I go about finding, say just the relative min with the function given?
• Nov 10th 2009, 11:13 PM
mr fantastic
Quote:

Originally Posted by jzellt
So, I guess I'm still a bit confused. How should I go about finding, say just the relative min with the function given?

Solve dy/dx = 0 for x. That gives the x-coordinates of all stationary points. Test the nature of the stationary points (use either the sign test or the second derivative test).

Your class notes and/or textbook should have several examples of this ....