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NDA2010MathematicsComplex NumberActual

If is a complex cube root of unity and x= ^2- -2 , then what is the value of x^2+4 x+7 ?

Options

  1. A-2
  2. B-1
  3. C0
  4. D1

Correct answer

C. 0

Step-by-step solution

x=w^2-w-2 Consider aligned & x^2+4 x+7=(-2 w-3)^2+4(-2 w-3)+7 & =4 w^2+4 w+4=4 (w^2+w+1 ) & =4 0=0 aligned

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