Let z 0 be a root of quadratic equation, x 2 + x + 1 = 0 .   If z = 3 + 6 i z 0 81 - 3 i z 0 93 , then…

Let z0 be a root of quadratic equation, x2+x+1=0.  If z=3+6iz081-3iz093 , then arg z is equal to:
  1. 0
  2. π4
  3. π6
  4. π3

Solution

z0=w or w2

When z0=w

z=3+6i×w81-3i×w93

=3+6i-3i=3+3i

When z0=w2

z=3+6i×w281-3i×w293

=3+6i-3i=3+3i

argz=tan-1ImzRez=tan-133=π4

Asked in: JEE Main 2019 (09 Jan Shift 2)

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