# Thread: Having problems finding a value for X using derivatives.

2. ## Re: Having problems finding a value for X using derivatives.

Originally Posted by Petrus
when u find a max and min point u derivate and set to zero then u put it on second derivate and se if its possitive i think its a min point and if its negative its max. wait for some1 to confirme im kinda tired so i can write wrong <.<
Yes, to find potential extrema, you equate the first derivative to zero and solve for x to get the critical number(s).

Then, evaluate the second derivative at these critical number(s), and if the result is positive you have a relative minimum, if it is negative you have a relative maximum, and if it is zero then there is no extremum at that point.

3. ## Re: Having problems finding a value for X using derivatives.

Originally Posted by MarkFL2
Yes, to find potential extrema, you equate the first derivative to zero and solve for x to get the critical number(s).

Then, evaluate the second derivative at these critical number(s), and if the result is positive you have a relative minimum, if it is negative you have a relative maximum, and if it is zero then there is no extremum at that point.
And to evaluate the minimum VALUE, substitute this critical number back into the original equation.

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