Solve the Equation by Making an Appropriate Substitution $$x ^ { - 2 } + 7 x ^ { - 1 } + 6 = 0$$

Multiple Choice

Solve the equation by making an appropriate substitution.
- $$x ^ { - 2 } + 7 x ^ { - 1 } + 6 = 0$$

A) $\left\{ - \frac { 1 } { 6 } , - 1 \right\}$
B) $\left\{ \frac { 1 } { 6 } , 1 \right\}$
C) $\{ 1,6 \}$
D) $\{ - 1 , - 6 \}$