Find the positive x-value where the function f(x)= 1/(3x^2+4) has an inflection point.?

Question

Calculus... I'm following the steps that would take to get the answer to this problem, but I think my math might be wrong somewhere along the line. If you think you could help me work this problem out, that would be great!

Answer 1

f'(x)=-6x/(3x^2+4)^2
f"(x)=6(9x^2-4)/(3x^2+4)^3
f"(x)=0
==>
x=2/3
or
x=-2/3
so
x=2/3