Use the derivative of $f ( x ) = 3 x ^ { 3 } + 9 x$ to determine any points on the graph of $f ( x )$ at which the tangent line is horizontal.
A) $( 1,12 )$
B) $( 1,12 )$ and $( - 1 , - 12 )$
C) $( 3,108 )$ and $( - 3,108 )$
D) $( 0,0 )$
E) $f ( x )$ has no points with a horizontal tangent line.

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The Answer of Use the derivative of $f ( x ) = 3 x ^ { 3 } + 9 x$ to determine any points on the graph of $f ( x )$ at which the tangent line is horizontal.
A) $( 1,12 )$
B) $( 1,12 )$ and $( - 1 , - 12 )$
C) $( 3,108 )$ and $( - 3,108 )$
D) $( 0,0 )$
E) $f ( x )$ has no points with a horizontal tangent line.

Use the Derivative Of f(x)=3x3+9xf ( x ) = 3 x ^ { 3 } + 9 xf(x)=3x3+9x

Use the Derivative Of $f ( x ) = 3 x ^ { 3 } + 9 x$