Find the Value of the Determinant $\left| \begin{array} { l l } \mathrm { a } & \mathrm { b } \\ \mathrm { b } & \mathrm { a } \end{array} \right|$

Multiple Choice

Find the value of the determinant.
- $\left| \begin{array} { l l } \mathrm { a } & \mathrm { b } \\ \mathrm { b } & \mathrm { a } \end{array} \right|$

A) $a ^ { 2 } + b ^ { 2 }$
B) $2 a b$
C) 0
D) $a ^ { 2 } - b ^ { 2 }$