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Find the value of k if for the complex numbers z1 and z2, z|1-z¯1z2|2-|z1-z2|2=k(1-|z1|2)(1-|z2|2)

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Question

Find the value of k if for the complex numbers z1 and z2, `|1 - barz_1z_2|^2 - |z_1 - z_2|^2 = k(1 - |z_1|^2)(1 - |"z"_2|^2)`

Sum
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Solution

L.H.S. = `|1 - barz_1z_2|^2 - |z_1 - z_2|^2`

= `(1 - barz_1z_2) (bar(1 - barz_1 z_2)) - (z_1 - z_2) (bar(z_1 - z_2))` 

= `(1 - barz_1 z_2) (1 - z_1 barz_2) - (z_1 - z_2)(barz_1 - barz_2)`

= `1 + z_1  barz_1  z_2barz_2 - z_1barz_1 - z_2barz_2`

= `1 + |z-1|^2 * |z_2|^2 - |z_1|^2 - |z_2|^2`

= `(1 - |z_1|^2)(1 - |z_2|^2)`

R.H.S. = `k(1 - |z_1|^2)(1 - |z_2|^2)`

⇒ k = 1

Hence, equating L.H.S. and R.H.S., we get k = 1.

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Chapter 5: Complex Numbers and Quadratic Equations - Solved Examples [Page 82]

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NCERT Exemplar Mathematics [English] Class 11
Chapter 5 Complex Numbers and Quadratic Equations
Solved Examples | Q 14 | Page 82

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