Home
Class 12
MATHS
Let z(1),z(2) and z(3) be non-zero com...

Let `z_(1),z_(2) and z_(3)` be non-zero complex numbers satisfying `z^(2)=bar(iz), where i=sqrt(-1).`
Consider the following statements:
1. `z_(1)z_(2)z_(3) ` is purely imaginary.
2. `z_(1)z_(2)+z_(2)z_(3)+z_(3)z_(1)` is purely real.
Which of the above statements is/are correct?

A

1 only

B

2 only

C

Both 1 and 2

D

neither 1 nor 2

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze the given equation and the statements related to the complex numbers \( z_1, z_2, z_3 \). ### Step 1: Understand the given equation The equation given is: \[ z^2 = i \bar{z} \] where \( \bar{z} \) is the conjugate of \( z \). ### Step 2: Express \( z \) in terms of its real and imaginary parts Let \( z = x + iy \), where \( x \) and \( y \) are real numbers. Then the conjugate \( \bar{z} = x - iy \). ### Step 3: Substitute \( z \) and \( \bar{z} \) into the equation Substituting into the equation gives: \[ (x + iy)^2 = i(x - iy) \] ### Step 4: Expand both sides Expanding the left side: \[ x^2 + 2xyi - y^2 = i(x - iy) \] Expanding the right side: \[ ix + y \] ### Step 5: Equate real and imaginary parts From the left side, we have: \[ x^2 - y^2 + 2xyi = ix + y \] This gives us two equations: 1. Real part: \( x^2 - y^2 = y \) 2. Imaginary part: \( 2xy = x \) ### Step 6: Solve the imaginary part equation From \( 2xy = x \), we can factor out \( x \): \[ x(2y - 1) = 0 \] This gives us two cases: 1. \( x = 0 \) 2. \( 2y - 1 = 0 \) which implies \( y = \frac{1}{2} \) ### Step 7: Analyze the cases **Case 1:** If \( x = 0 \): - Substitute into the real part equation: \[ 0 - y^2 = y \implies y^2 + y = 0 \implies y(y + 1) = 0 \] Thus, \( y = 0 \) or \( y = -1 \). This gives us two complex numbers: - \( z_1 = 0 \) (not allowed since \( z \) is non-zero) - \( z_2 = -i \) **Case 2:** If \( y = \frac{1}{2} \): - Substitute into the real part equation: \[ x^2 - \left(\frac{1}{2}\right)^2 = \frac{1}{2} \implies x^2 - \frac{1}{4} = \frac{1}{2} \implies x^2 = \frac{3}{4} \] Thus, \( x = \pm \frac{\sqrt{3}}{2} \). This gives us two more complex numbers: - \( z_2 = \frac{\sqrt{3}}{2} + \frac{i}{2} \) - \( z_3 = -\frac{\sqrt{3}}{2} + \frac{i}{2} \) ### Step 8: List the complex numbers The three complex numbers are: - \( z_1 = -i \) - \( z_2 = \frac{\sqrt{3}}{2} + \frac{i}{2} \) - \( z_3 = -\frac{\sqrt{3}}{2} + \frac{i}{2} \) ### Step 9: Verify the statements 1. **Statement 1:** \( z_1 z_2 z_3 \) is purely imaginary. \[ z_1 z_2 z_3 = (-i) \left(\frac{\sqrt{3}}{2} + \frac{i}{2}\right) \left(-\frac{\sqrt{3}}{2} + \frac{i}{2}\right) \] The product \( z_2 z_3 = \left(\frac{\sqrt{3}}{2}\right)^2 + \left(\frac{1}{2}\right)^2 = \frac{3}{4} + \frac{1}{4} = 1 \). Thus, \( z_1 z_2 z_3 = -i \cdot 1 = -i \), which is purely imaginary. 2. **Statement 2:** \( z_1 z_2 + z_2 z_3 + z_3 z_1 \) is purely real. Calculate each product: - \( z_1 z_2 = -i \left(\frac{\sqrt{3}}{2} + \frac{i}{2}\right) = -\frac{\sqrt{3}}{2}i - \frac{1}{2} \) - \( z_2 z_3 = \left(\frac{\sqrt{3}}{2} + \frac{i}{2}\right) \left(-\frac{\sqrt{3}}{2} + \frac{i}{2}\right) = 1 \) - \( z_3 z_1 = -\frac{\sqrt{3}}{2} + \frac{i}{2} \cdot -i = \frac{\sqrt{3}}{2} + \frac{1}{2} \) Adding these gives: \[ z_1 z_2 + z_2 z_3 + z_3 z_1 = -\frac{1}{2} + 1 + \frac{1}{2} = 1 \] which is purely real. ### Conclusion Both statements are true.

To solve the problem, we need to analyze the given equation and the statements related to the complex numbers \( z_1, z_2, z_3 \). ### Step 1: Understand the given equation The equation given is: \[ z^2 = i \bar{z} \] where \( \bar{z} \) is the conjugate of \( z \). ...
Promotional Banner

Topper's Solved these Questions

  • CIRCLE

    NDA PREVIOUS YEARS|Exercise MCQs|40 Videos
  • CONICS - PARABOLA, ELLIPSE & HYPERBOLA

    NDA PREVIOUS YEARS|Exercise MATH|62 Videos

Similar Questions

Explore conceptually related problems

Let z_(1),z_(2) and z_(3) be non-zero complex numbers satisfying z^(2)=bar(iz), where i=sqrt(-1). What is z_(1)+z_(2)+z_(3) equal to ?

If (5z_(1))/(7z_(2)) is purely imaginary then |(2z_(1)+3z_(2))/(2z_(1)-3z_(2))|=

If (2z_(1))/(3z_(2)) is purely imaginary number, then |(z_(1)-z_(2))/(z_(1)+z_(2))|^(4) is equal to

If (3 z_(1))/(5 z_(2)) is purely imaginary, then |(2z_(1)-z_(2))/(2z_(1) + z_(2))| is equal to _________

" If "(z_(2))/(z_(1))" is purely imaginary then "|(6z_(1)-8z_(2))/(4z_(2)+3z_(1))|" is equal to."

NDA PREVIOUS YEARS-COMPLEX NUMBERS-Multiple choice question
  1. If z=x+iy=((1)/(sqrt2)-(i)/(sqrt2))^(-25), where i=sqrt(-1), then wha...

    Text Solution

    |

  2. Let z(1),z(2) and z(3) be non-zero complex numbers satisfying z^(2)=...

    Text Solution

    |

  3. Let z(1),z(2) and z(3) be non-zero complex numbers satisfying z^(2)=...

    Text Solution

    |

  4. Let z be a complex number satisfying |(z-4)/(z-8)|=1and|(z)/(z-2)|=...

    Text Solution

    |

  5. Let z be a complex number satisfying |(z-4)/(z-8)|=1and|(z)/(z-2)|=...

    Text Solution

    |

  6. Suppose omega(1) and omega(2) are two distinct cube roots of unity ...

    Text Solution

    |

  7. What is omega^(100)+omega^(200)+omega^(300) equal to, where omega is t...

    Text Solution

    |

  8. If Re((z-1)/(z+1))=0 where z=x+iy is a complex number, then which one ...

    Text Solution

    |

  9. If z=((sqrt3)/(2)+(i)/(2))^(107)+((sqrt3)/(2)-(i)/(2))^(107), then wha...

    Text Solution

    |

  10. What is the number of distinct solutions of the equation z^2+|z|=0 (wh...

    Text Solution

    |

  11. What is sqrt((1+(omega)^(2))/(1+(omega))) equal to, where omega is the...

    Text Solution

    |

  12. The value of i^(2n)+i^(2n+1)+i^(2n+2)+i^(2n+3), where i=sqrt(-1), is

    Text Solution

    |

  13. What is the value of ((1=-+isqrt3)/(2))^(3n)+((-1+isqrt3)/(2))^(3n) wh...

    Text Solution

    |

  14. The modulus and principle argument of the complex number (1+2i)/(1-(1...

    Text Solution

    |

  15. IF |z+4|le3, then the maximum value of |z+1| is

    Text Solution

    |

  16. The number of roots of the equation z^2 = 2 barz is

    Text Solution

    |

  17. If A=[{:(4i-6,10i),(14i,6+4i):}]and k(1)/(ki), where i- sqrt(-1), then...

    Text Solution

    |

  18. The smallest positive integer n for which ((1+i)/(1-i))^n=i is 8 (b) 1...

    Text Solution

    |

  19. Geometrically Re(z^(2)-i)=2,where i=sqrt(-1) and Re is the real part, ...

    Text Solution

    |

  20. What is the principal argument of (-1-i), where i=sqrt(-1) ?

    Text Solution

    |