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Let `z in C` be such that `|z| lt 1 `.If `omega =(5+3z)/(5(1-z)` thenA. `4 Im ( omega) gt 5`B. `5 Re (omega) gt 1`C. `5 Im(omega) lt 1 `D. |
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Answer» Correct Answer - B Given complex number `omega=(5+3z)/(5(1-z))` `rArr 5 omega -5 omega z=5+3z` `rarr (3+5 omega)z=5 omega-5` `rArr |3+5 omega||z|=|5 omega- 5|` [applying modulus both sides and `|z_1z_2|=|z_2||z_2|]` `therefore | z| lt 1 ` `therefore |3+5 omega| gt |5 omega - 5|" "["from Eq.(i)"]` `rArr " "|omega+3/5| gt | omega-1|` Let `omega` =x+iy, then `(x+3/5)^2+y^2 gt (x-1)^2+y^2` `rArr x^2+9/25+6/5 x lt x^2 +1 -2x` `rArr 16x/5 gt 16/25 rArr x gt 1/5 rArr lt 1` `rArr 5 Re(omega ) gt 1` |
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