How can I find the number of complex numbers satisfying |z|=z+1+2i?

Click For Summary
SUMMARY

The discussion centers on solving the equation |z| = z + 1 + 2i for complex numbers. The user defines z as x + iy and derives the equation 2x + 4y + 5 = 0 after equating the moduli. A critical insight is that since the absolute value of a complex number is real, the imaginary part must equal -2, leading to the conclusion that z must be of the form z = x - 2i. The final task is to determine how many points on the line 2x + 4y + 5 = 0 also satisfy y = -2.

PREREQUISITES
  • Understanding of complex numbers and their properties
  • Familiarity with modulus and absolute value of complex numbers
  • Basic algebraic manipulation and solving linear equations
  • Knowledge of the geometric interpretation of complex numbers
NEXT STEPS
  • Explore the geometric representation of complex numbers on the Argand plane
  • Study the properties of complex modulus and its implications
  • Learn how to solve linear equations in two variables
  • Investigate alternative methods for solving complex equations, such as polar coordinates
USEFUL FOR

Mathematics students, educators, and anyone interested in complex analysis or solving equations involving complex numbers.

utkarshakash
Gold Member
Messages
852
Reaction score
13

Homework Statement


Find the number of complex numbers satisfying |z|=z+1+2i


Homework Equations




The Attempt at a Solution


Let z=x+iy
|x+iy| = (x+1)+i(2+y)
Squaring and taking modulus
|\sqrt{x^{2}+y^{2}}|^{2} = |(x+1)+i(2+y)|^{2}
x^{2}+y^{2} = (x+1)^{2}+(2+y)^{2}
Rearranging and simplifying I get
2x+4y+5=0

Now what to do next? Also Is there any other way to solve this question?
 
Physics news on Phys.org
You seem to have missed an important point- the absolute value of a complex number is real. Since the left side of the equation is real, the right side must be. z must be of the form z= x- 2i so that z+ 1+ 2i= x+1. What you did was correct but how many points on the line 2x+ 4y+ 5= 0 also satisfy y= -2?
 

Similar threads

  • · Replies 10 ·
Replies
10
Views
2K
  • · Replies 20 ·
Replies
20
Views
3K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 19 ·
Replies
19
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
Replies
31
Views
4K
  • · Replies 12 ·
Replies
12
Views
3K