Got Homework?
Connect with other students for help. It's a free community.
Here's the question you clicked on:
 0 viewing
ksandoval
Group Title
use analytic methods to find the extreme values of f(x)= (1/x) + lnx on the interval 0.5 ≤ x ≤ 4 and where they occur
 2 years ago
 2 years ago
ksandoval Group Title
use analytic methods to find the extreme values of f(x)= (1/x) + lnx on the interval 0.5 ≤ x ≤ 4 and where they occur
 2 years ago
 2 years ago

This Question is Closed

ksandoval Group TitleBest ResponseYou've already chosen the best response.0
and i know that the derivative is f'(x) = 1/x^2 + 1/x but i dont know where to go from there... lol
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
Where do extreme values occur?
 2 years ago

ksandoval Group TitleBest ResponseYou've already chosen the best response.0
i dont know thats what i need help finding.. lol. i just dont know how to find them.
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
okay, so in theory, extreme values will occur where the derivative of the function is equal to zero (i.e. a horizontal slope where there is maxima or minima), and they also occur where the derivative is undefined.
 2 years ago

ksandoval Group TitleBest ResponseYou've already chosen the best response.0
okay sooo i set the derivative equal to zero...
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
and...?
 2 years ago

ksandoval Group TitleBest ResponseYou've already chosen the best response.0
well i mean plugging in 1 for x would give you zero.
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
okay, so 1 is one of our critical points
 2 years ago

ksandoval Group TitleBest ResponseYou've already chosen the best response.0
now what do we do?
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
Where is f'(x) = 1/x^2 + 1/x undefined?
 2 years ago

ksandoval Group TitleBest ResponseYou've already chosen the best response.0
when x = 0?
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
exactly, but if you would notice in the question it gave us restrictions of 0.5 ≤ x ≤ 4, so we dont take 0 into account... So our critical point is 1
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
http://screencast.com/t/LJnPiplk
 2 years ago

ksandoval Group TitleBest ResponseYou've already chosen the best response.0
oooh ok. so for the answer it says: max value is 1/4 + ln4 at x = 4 min value is 1 at x = 1 local max at (1/2, 2  ln2) how did they get the max value and local max?
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
Well for the max value, they just put the biggest number they could, 4, into the function, they chose 4 because of the restrictions 0.5 ≤ x ≤ 4... 4 is the biggest number, i.e. giving the biggest value.
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
there is no local max... so i'm not sure where they got that.. might want to ask your teacher.
 2 years ago

ksandoval Group TitleBest ResponseYou've already chosen the best response.0
oh.. ok. and how do they know that 1 is the min value? this is confusing for me ):
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
We already got that the minimum is at x = 1
 2 years ago

ksandoval Group TitleBest ResponseYou've already chosen the best response.0
yea but how do you know its the minimum? :\
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
We know it is the minimum because at that point, the derivative = 0, this is the lowest point on the curve.
 2 years ago

ksandoval Group TitleBest ResponseYou've already chosen the best response.0
thank you
 2 years ago
See more questions >>>
Your question is ready. Sign up for free to start getting answers.
spraguer
(Moderator)
5
→ View Detailed Profile
is replying to Can someone tell me what button the professor is hitting...
23
 Teamwork 19 Teammate
 Problem Solving 19 Hero
 Engagement 19 Mad Hatter
 You have blocked this person.
 ✔ You're a fan Checking fan status...
Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.