4-1.Complex numbers
easy

જો ${z_1}$ અને ${z_2}$ બે સંકર સંખ્યા હોય ,તો $|{z_1} + {z_2}{|^2}$ $ + |{z_1} - {z_2}{|^2}$ =...

A

$2|{z_1}{|^2}\,|{z_2}{|^2}$

B

$2|{z_1}{|^2} + \,2\,\,|{z_2}{|^2}$

C

$|{z_1}{|^2} + \,|{z_2}{|^2}$

D

$2|{z_1}|\,\,|{z_2}|$

Solution

(b) $|{z_1} + {z_2}{|^2} + |{z_1} – {z_2}{|^2}$
$ = {({x_1} + {x_2})^2} + {({y_1} + {y_2})^2} + {({x_1} – {x_2})^2} + {({y_1} – {y_2})^2}$
$ = 2(x_1^2) + 2(y_1^2) + 2(x_2^2) + 2(y_2^2) = 2|{z_1}{|^2} + 2|{z_2}{|^2}$

Standard 11
Mathematics

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