Let A = z in C : |z - 2| ≤ 4 and B = z in C : |z - 2| + |z + 2| = 5. Then the max |z₁ - z₂| : z₁ in A and z₂ in B is

Solution & Explanation

Core Logic

Analyze region A: |z - 2| ≤ 4 represents a solid disk with center (2, 0) and radius R=4. Its rightmost point on the real axis is (6, 0) and leftmost is (-2, 0).

Analyze locus B: |z - 2| + |z + 2| = 5 represents an ellipse with foci at (2, 0) and (-2, 0), and major axis length 2a = 5 ⇒ a = (5)/(2). The equation of the ellipse is (x²)/((5/2)²) + (y²)/(b²) = 1. Its leftmost vertex is at (-(5)/(2), 0).

Complex geometry loci map
Complex geometry loci map

Execution

To maximize |z₁ - z₂|, we need the maximum geometric distance between any point in the disk A and any point on the ellipse B. By visualizing the placement on the coordinate plane: The rightmost point of the circle A is z₁ = 6. The leftmost point of the ellipse B is z₂ = -(5)/(2). The distance between them is the maximum horizontal span since both shapes are symmetric around the real axis and their extremes occur on the real axis.

|z₁ - z₂| = 6 - (-(5)/(2)) = 6 + (5)/(2) = (17)/(2)
Pattern Recognition

Maximum distance problems between loci in the complex plane almost always resolve to finding the extreme diametric points along their shared axis of symmetry (usually the real axis).

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Reference Study Guides

More Complex Numbers and Quadratic Equations Previous-Year Questions — Page 9

Q26 jee_main_2024_31_jan_morning Properties of Modulus and Argument
If α denotes the number of solutions of |1 - i|^x = 2^x and β = ((|z|)/( (z))), where z = (π)/(4) (1 + i)⁴ ( 1 - √(π) i√(π) + i + √(π) - i1 + √(π) i), i = √(-1), then the distance of the point (α, β) from the line 4x - 3y = 7 is
Numerical Answer. Answer: 3 to 3

Solution

Core Logic
|1 - i|^x = 2^x (√(2))^x = 2^x 2x/2 = 2^x

This implies (x)/(2) = x x = 0. There is exactly 1 solution, so α = 1.

Step 1: Simplify complex number z
(1+i)⁴ = ((1+i)²)² = (1 + i² + 2i)² = (2i)² = -4

Thus, z = -π ( (1-√(π)i)(√(π)-i)π + 1 + (√(π)-i)(1-√(π)i)1 + π )

Step 2: Simplify Bracket

Let's expand the terms directly: z = (π)/(4)(-4) [ √(π) - π i - i - √(π)π + 1 + √(π) - i - π i - √(π)1 + π ]

= -π [ (-i(π+1))/(π+1) + (-i(π+1))/(π+1) ] = -π [ -i - i ] = 2π i
Step 3: Find beta

For z = 2π i: |z| = 2π and (z) = (π)/(2).

β = (|z|)/( (z)) = (2π)/(π/2) = 4
Step 4: Distance from Line

Distance of point (α, β) = (1, 4) from the line 4x - 3y - 7 = 0:

D = |4(1) - 3(4) - 7|√(4² + (-3)²) = (|4 - 12 - 7|)/(5) = (|-15|)/(5) = 3
Chapter Mix

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