February 21, 2017

Homework Help: Inflection points

Posted by Kay on Tuesday, November 17, 2009 at 12:14am.

Consider the function f(x)=12x^5+30x^4–300x^3+2. f(x) has inflection points at (reading from left to right) x=D,E, and F. where D is___, E is____, and F is____.

I took the second derivative of the function and got 120x(2x^2+3x-15). From that I set it to equal and tried finding x. One is obviously zero.

Then I tried using the quadratic formula to get the other two x's. I got [-3 + sqrt(129)]/4 and [-3 - sqrt(129)]/4

However I plugged the answer into my online homework site and it says that is incorrect. Can someone help?

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