Find the Least Common Denominator of the Rational Expressions $\frac { 1 } { - 3 x }$

Multiple Choice

Find the least common denominator of the rational expressions.
- $\frac { 1 } { - 3 x }$ and $\frac { 2 } { x ^ { 2 } + 7 x }$

A) $- 3 x ( x + 7 )$
B) $- 3 x + 7$
C) $- 3 x ^ { 2 } + 2$
D) $- 3 x ^ { 2 } + 7$