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Let z1 = 2 – i, z2 = –2 + i. Find Re(z1z2z¯1)

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Question

Let z1 = 2 – i, z2 = –2 + i. Find Re`((z_1z_2)/barz_1)`

Sum
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Solution

z1 = 2 – i, z2 = –2 + i

`((z_1z_2)/barz_1)  =  ((2 - i)(-2 +i))/(2 -i) = (-(2 - i)(2 -i))/(2 + i)`

= `- (2-i)^2/(2 + i)  = (- (4 + i^2 - 4i))/(2 + i)`

= `(-(4  - 1 -  4i))/((2 + i)) = -(3 - 4i)/(2 + i)`

= `-(3 - 4i)/(2 + i)  xx (2 - i)/(2 - i)`

= `(-  6  - 4i^2  + 3i  + 8i)/(4 - i^2)  =  (-  6  + 4  +  11i)/(4 + 1)`

= `(- 2 + 11i)/5  = - 2/5  + 11/5 i`

Re`((z_1z_2)/barz_1)  = - 2/5`

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Chapter 4: Complex Numbers and Quadratic Equations - Miscellaneous Exercise [Page 86]

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NCERT Mathematics [English] Class 11
Chapter 4 Complex Numbers and Quadratic Equations
Miscellaneous Exercise | Q 7. (i) | Page 86

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