Differentiate $\frac { 2 x - \left( x ^ { 2 } + 1 \right) ^ { 7 } } { 3 }$

Multiple Choice

Differentiate.
-f(x) = $\frac { 2 x - \left( x ^ { 2 } + 1 \right) ^ { 7 } } { 3 }$

A) f'(x) = $f ^ { \prime } ( x ) = 2 - 7 \left( x ^ { 2 } + 1 \right) ^ { 6 }$
B) f'(x) = $\frac { 2 } { 3 }$ - $\frac { 14 } { 3 }$ x( $x ^ { 2 }$ + 1 $) ^6$
C) f'(x) = $\frac { 2 - x } { 3 \left( x ^ { 2 } + 1 \right) ^ { 6 } }$
D) none of these