Home
Class 12
MATHS
Let p and q are complex numbers such tha...

Let `p` and `q` are complex numbers such that `|p|+|q| lt 1`. If `z_(1)` and `z_(2)` are the roots of the `z^(2)+pz+q=0`, then which one of the following is correct ?

A

`|z_(1)| lt 1` and `|z_(2)| lt 1`

B

`|z_(1)| gt 1` and `|z_(2)| gt 1`

C

If `|z_(1)| lt 1`, then `|z_(2)| gt 1` and vice versa

D

Nothing definite can be said

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze the quadratic equation given by \( z^2 + pz + q = 0 \) and the properties of its roots \( z_1 \) and \( z_2 \). ### Step-by-Step Solution: 1. **Identify the Roots**: The roots of the quadratic equation \( z^2 + pz + q = 0 \) can be expressed using Vieta's formulas: - Sum of the roots: \( z_1 + z_2 = -p \) - Product of the roots: \( z_1 z_2 = q \) 2. **Take Modulus of the Roots**: Taking the modulus of the sum of the roots: \[ |z_1 + z_2| = |-p| = |p| \] Taking the modulus of the product of the roots: \[ |z_1 z_2| = |q| \] 3. **Use the Given Condition**: We know from the problem that: \[ |p| + |q| < 1 \] 4. **Apply the Triangle Inequality**: From the triangle inequality, we have: \[ |z_1 + z_2| \leq |z_1| + |z_2| \] Substituting the value from step 2: \[ |p| \leq |z_1| + |z_2| \] 5. **Express \( |z_1| + |z_2| \)**: We can also express \( |z_1| + |z_2| \) in terms of \( |z_1 z_2| \): \[ |z_1 + z_2| = |p| \quad \text{and} \quad |z_1 z_2| = |q| \] Thus, we can write: \[ |z_1| + |z_2| \geq |p| - |z_1 z_2| = |p| - |q| \] 6. **Combine the Inequalities**: From the earlier step, we have: \[ |p| \leq |z_1| + |z_2| \quad \text{and} \quad |z_1| + |z_2| \geq |p| - |q| \] Combining these gives: \[ |p| + |q| < 1 \] 7. **Conclude the Modulus of Roots**: Since \( |p| + |q| < 1 \), we can conclude that: \[ |z_1| < 1 \quad \text{and} \quad |z_2| < 1 \] ### Final Result: Thus, we can conclude that both roots \( z_1 \) and \( z_2 \) have moduli less than 1.

To solve the problem, we need to analyze the quadratic equation given by \( z^2 + pz + q = 0 \) and the properties of its roots \( z_1 \) and \( z_2 \). ### Step-by-Step Solution: 1. **Identify the Roots**: The roots of the quadratic equation \( z^2 + pz + q = 0 \) can be expressed using Vieta's formulas: - Sum of the roots: \( z_1 + z_2 = -p \) - Product of the roots: \( z_1 z_2 = q \) ...
Promotional Banner

Topper's Solved these Questions

  • COMPLEX NUMBERS

    CENGAGE ENGLISH|Exercise Multiple Correct Answer|11 Videos
  • COMPLEX NUMBERS

    CENGAGE ENGLISH|Exercise Comprehension|11 Videos
  • CIRCLES

    CENGAGE ENGLISH|Exercise Comprehension Type|8 Videos
  • CONIC SECTIONS

    CENGAGE ENGLISH|Exercise All Questions|101 Videos

Similar Questions

Explore conceptually related problems

If z complex number satisfying |z-1| = 1 , then which of the following is correct

If z_(1) and z_(2) are two complex numbers such that |(z_(1)-z_(2))/(1-barz_(1)z_(2))|=1 , then which one of the following is true?

Let z_(1),z_(2) be two complex numbers such that z_(1)+z_(2) and z_(1)z_(2) both are real, then

If z_(1) and z_(2) are the complex roots of the equation (x-3)^(3) + 1=0 , then z_(1) +z_(2) equal to

If z_(1) and z_(2) are two complex numbers such that |(z_(1)-z_(2))/(z_(1)+z_(2))|=1 , then

If z_(1) and z_(2) are two complex numbers such that |z_(1)|= |z_(2)| , then is it necessary that z_(1) = z_(2)

Let a , b , c be distinct complex numbers with |a|=|b|=|c|=1 and z_(1) , z_(2) be the roots of the equation az^(2)+bz+c=0 with |z_(1)|=1 . Let P and Q represent the complex numbers z_(1) and z_(2) in the Argand plane with /_POQ=theta , o^(@) lt 180^(@) (where O being the origin).Then

Let z_(1),z_(2) be two complex numbers such that |z_(1)+z_(2)|=|z_(1)|+|z_(2)| . Then,

If z_(1) , z_(2), z_(3) are three complex numbers in A.P., then they lie on :

Fill in the blanks. If z_(1) " and " z_(2) are complex numbers such that z_(1) +z_(2) is a real number, then z_(1) = ….