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____.

Question

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?

Writeacher · Answer

Assistance needed. Please type your subject in the School Subject box. Any other words are likely to delay responses from a teacher who knows that subject well.

bobpursley · Answer

I agree with you.

Kay · Answer

Writeacher, thanks for the tip...I was never really sure whether I was supposed to type my actual class subject or the subject material. If it's ok, I might submit this question again with a different school subject.