Find F '(X)if $f ( x ) = e ^ { 6 x } \cos 4 x$

Multiple Choice

Find f '(x) if $f ( x ) = e ^ { 6 x } \cos 4 x$ .

A) $\left. - 24 e ^ { 6 x } \sin 4 x \right)$
B) $24 e ^ { 6 x } ( \cos 4 x - \sin 4 x )$
C) $e ^ { 6 x } ( 6 \cos 4 x - 4 \sin 4 x )$
D) $e ^ { 6 x } ( 6 \cos 4 x - 6 \sin 4 x )$