# Simple Concavity Question

• Nov 19th 2011, 12:24 PM
poipoipoi10
Simple Concavity Question
The function y=f(x) has second derivative http://www.uoguelph.ca/mapleta/tmp/o...njmchmocnm.gif . Find the intervals on which y=f(x) is concave down. Give your answer using interval notation. Use infinity U for union if required.

I know this is a pretty simple question, but I couldn't make it to this lecture. I'm pretty sure your supposed to find the points of inflection and then put them in a table to find where it's concave down but every time I try this I get an incorrect answer. Thanks Alot!
• Nov 19th 2011, 01:09 PM
skeeter
Re: Simple Concavity Question
Quote:

Originally Posted by poipoipoi10
The function y=f(x) has second derivative http://www.uoguelph.ca/mapleta/tmp/o...njmchmocnm.gif . Find the intervals on which y=f(x) is concave down. Give your answer using interval notation. Use infinity U for union if required.

I know this is a pretty simple question, but I couldn't make it to this lecture. I'm pretty sure your supposed to find the points of inflection and then put them in a table to find where it's concave down but every time I try this I get an incorrect answer. Thanks Alot!

set f''(x) = 0 , plot the zeros on a number line, and evaluate f''(x) for a single value of x from each interval between zeros ... f(x) is concave down on those intervals where f''(x) < 0.
• Nov 19th 2011, 01:10 PM
poipoipoi10
Re: Simple Concavity Question
Thanks!