Answer
$$\eqalign{
& {\text{Inflection point }}\left( {0,4} \right) \cr
& {\text{Concave downward}}:{\text{ }}\left( { - \infty ,\infty } \right) \cr} $$
Work Step by Step
$$\eqalign{
& f\left( x \right) = 4 - x - 3{x^4} \cr
& {\text{Calculate the second derivative}} \cr
& f'\left( x \right) = \frac{d}{{dx}}\left[ {4 - x - 3{x^4}} \right] \cr
& f'\left( x \right) = - 1 - 12{x^3} \cr
& f''\left( x \right) = \frac{d}{{dx}}\left[ { - 1 - 12{x^3}} \right] \cr
& f''\left( x \right) = - 36{x^2} \cr
& {\text{Set }}f''\left( x \right) = 0 \cr
& - 36{x^2} = 0 \cr
& x = 0 \cr
& {\text{Set the intervals }}\left( { - \infty ,0} \right),\left( {0,\infty } \right) \cr
& {\text{Making a table of values }}\left( {{\text{See examples on page 188 }}} \right) \cr} $$
\[\boxed{\begin{array}{*{20}{c}}
{{\text{Interval}}}&{\left( { - \infty ,0} \right)}&{\left( {0,\infty } \right)} \\
{{\text{Test Value}}}&{x = - 5}&{x = 5} \\
{{\text{Sign of }}f''\left( x \right)}&{f''\left( { - 5} \right) = - 900 < 0}&{f''\left( 5 \right) = - 900 < 0} \\
{{\text{Conclusion}}}&{{\text{Concave downward}}}&{{\text{Concave downward}}}
\end{array}}\]
$$\eqalign{
& {\text{The inflection point occurs at }}x = 0 \cr
& f\left( 0 \right) = 4 - \left( 0 \right) - 3{\left( 0 \right)^4} \cr
& {\text{Inflection point }}\left( {0,4} \right) \cr
& {\text{Concave downward}}:{\text{ }}\left( { - \infty ,\infty } \right) \cr} $$
