Find the Integrating Factor of the Differential Equation $\left( 3 x ^ { 3 } + 2 y \right) d x - x d y = 0 \text { that is }$

Multiple Choice

Find the integrating factor of the differential equation $\left( 3 x ^ { 3 } + 2 y \right) d x - x d y = 0 \text { that is }$ a function of x or y alone.

A) $\frac { 1 } { x ^ { - 3 } }$
B) $- \frac { 3 } { x }$
C) $- \frac { 2 } { x }$
D) $\frac { 1 } { x ^ { - 4 } }$
E) $\frac { 1 } { x ^ { 3 } }$