Determine the Most Efficient Method to Use When Solving a Quadratic

Multiple Choice

Determine the Most Efficient Method to Use When Solving a Quadratic Equation
Solve the equation by the method of your choice.
- $x ^ { 2 } + 12 x + 15 = 0$

A) $\{ - 6 - \sqrt { 21 } , - 6 + \sqrt { 21 } \}$
B) $\{ 6 + \sqrt { 21 } \}$
C) $\{ 6 - \sqrt { 15 } , 6 + \sqrt { 15 } \}$
D) $\{ - 12 + \sqrt { 15 } \}$