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COMEDK2015MathematicsComplex Number

If the conjugate of (x+i y)(1-2 i) is 1+i , then

Options

  1. Ax-i y= 1-i 1-2 i
  2. Bx+i y= 1-i 1-2 i
  3. Cx= 1 5
  4. Dx=- 1 5

Correct answer

B. x+i y= 1-i 1-2 i

Step-by-step solution

We have, (x+i y)(1-2 i) =1+i (x+i y)(1-2 i) =1+i (x-i y)(1+2 i)=1+i x-i y= 1+i 1+2 i x-i y = ( 1+i 1+2 i ) = 1-i 1-2 i x+i y= 1-i 1-2 i

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