Physics Forums (http://www.physicsforums.com/index.php)
-   Precalculus Mathematics Homework (http://www.physicsforums.com/forumdisplay.php?f=155)
-   -   Find min, max of an unfamiliar function (http://www.physicsforums.com/showthread.php?t=581610)

 truongson243 Feb26-12 03:22 PM

Find min, max of an unfamiliar function

1. The problem statement, all variables and given/known data

For every x over ℝ, find min, max of following expression

2. Relevant equations

y=8x4/(x2+1)2+4x/(x2+1)+1

3. The attempt at a solution
I've graphed it but it's really complex. How can I find that points? Thank you so much :)

 Mark44 Feb26-12 05:28 PM

Re: Find min, max of an unfamiliar function

Quote:
 Quote by truongson243 (Post 3785716) 1. The problem statement, all variables and given/known data For every x over ℝ, find min, max of following expression
"every x over ℝ" - this shows up as a box in my browser.
Quote:
 Quote by truongson243 (Post 3785716) 2. Relevant equations y=8x4/(x2+1)2+4x/(x2+1)+1
I'm assuming that you wrote the right side correctly, where there are three terms, with 1 being a term by itself. Rewrite the right side as a single rational expression. What is the least common denominator?
Quote:
 Quote by truongson243 (Post 3785716) 3. The attempt at a solution I've graphed it but it's really complex. How can I find that points? Thank you so much :)

 Ray Vickson Feb26-12 07:28 PM

Re: Find min, max of an unfamiliar function

Quote:
 Quote by truongson243 (Post 3785716) 1. The problem statement, all variables and given/known data For every x over ℝ, find min, max of following expression 2. Relevant equations y=8x4/(x2+1)2+4x/(x2+1)+1 3. The attempt at a solution I've graphed it but it's really complex. How can I find that points? Thank you so much :)
You need to use Calculus, setting the derivative to zero. That gives you a 4th degree polynomial to solve; its two real roots correspond to the max and min. (They are the roots of the polynomial x4 - 8x3 - 1.)

RGV

 All times are GMT -5. The time now is 10:58 AM.