MathematicsEasy53×since 2002Q3152If z−αz+α(α∈R){{z - \alpha } \over {z + \alpha }}\left( {\alpha \in R} \right)z+αz−α(α∈R) is a purely imaginary number and | z | = 2, then a value of α\alphaα is :A12{1 \over 2}21B2\sqrt 22C2D1Check answerSkip