Answer
All the polynomials of the form:
$$ f(x)=a_0+a_1x+a_2x^2.$$
Work Step by Step
Any polynomial $ f(x)$ of degree $2$ is given by
$$ f(x)=a_0+a_1x+a_2x^2.$$
Now, we have
$$ f'(x)=a_1+2a_2x, \quad f''(x)=2a_2$$
and hence $ f'''(x)=0$ for all $ x $.
