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4-1.Complex numbers
medium
यदि $\alpha $ व $\beta $ भिन्न सम्मिश्र संख्याएँ इस प्रकार हैं कि $|\beta | = 1$, तब $\left| {\frac{{\beta - \alpha }}{{1 - \alpha \beta }}} \right|$ =
A
$0$
B
$3$
C
$1$
D
$2$
(IIT-1992)
Solution
(c) $\left| {\frac{{\beta – \alpha }}{{1 – \overline \alpha \beta }}} \right| = \left| {\frac{{\beta – \alpha }}{{\beta \bar \beta – \overline \alpha \beta }}} \right| = \left| {\frac{{\beta – \alpha }}{{\beta (\bar \beta – \overline \alpha )}}} \right|$
$ = \frac{1}{{|\beta |}}\left| {\frac{{\beta – \alpha }}{{(\overline {\beta – \alpha } )}}} \right| = \frac{1}{{|\beta |}} = 1$
Standard 11
Mathematics