If $$\frac{a}{b}{\text{ + }}\frac{b}{a}{\text{ = 2,}}$$    then the value of (a - b) is = ?

$$\eqalign{ & {\text{Given,}}\frac{a}{b}{\text{ + }}\frac{b}{a}{\text{ = 2}} \cr & \Rightarrow \frac{{{a^2} + {b^2}}}{{ab}} = 2 \cr & \Rightarrow {a^2} + {b^2} = 2ab \cr & \Rightarrow {a^2} + {b^2} - 2ab = 0 \cr & \Rightarrow {\left( {a - b} \right)^2} = 0 \cr & \Rightarrow \left( {a - b} \right){\text{ = 0 }} \cr} $$