$$\begin{aligned}
& a = \frac { x } { x - y } \\
& b = \frac { y } { x + y }
\end{aligned}$$ Given this, what is the value of the expression $\frac { a + b - 1 } { a \cdot b }$? A) $- 2$ B) $- 1$ C) $0$ D) $1$ E) $2$
$$\begin{aligned}
& a = \frac { x } { x - y } \\
& b = \frac { y } { x + y }
\end{aligned}$$
Given this, what is the value of the expression $\frac { a + b - 1 } { a \cdot b }$?\\
A) $- 2$\\
B) $- 1$\\
C) $0$\\
D) $1$\\
E) $2$