Let z₁ and z₂ be two complex numbers such that z₁ + z₂ = 5 and z₁³ + z₂³ = 20 + 15i. Then |z₁⁴ + z₂⁴| equals-

Solution & Explanation

Related Formula
a³+b³ = (a+b)³ - 3ab(a+b) a²+b² = (a+b)² - 2ab a⁴+b⁴ = (a²+b²)² - 2a²b²
Core Logic

Given z₁+z₂=5 and z₁³+z₂³=20+15i.

z₁³+z₂³ = (z₁+z₂)³ - 3z₁z₂(z₁+z₂) 20+15i = 125 - 15z₁z₂ 15z₁z₂ = 105 - 15i z₁z₂ = 7-i

Now, compute z₁²+z₂²:

z₁²+z₂² = (z₁+z₂)² - 2z₁z₂ = 25 - 2(7-i) = 11+2i

Now, compute z₁⁴+z₂⁴:

z₁⁴+z₂⁴ = (z₁²+z₂²)² - 2(z₁z₂)² = (11+2i)² - 2(7-i)² = (121 - 4 + 44i) - 2(49 - 1 - 14i) = 117 + 44i - 2(48 - 14i) = 117 + 44i - 96 + 28i = 21 + 72i

Finally, find magnitude:

|z₁⁴+z₂⁴| = |21+72i| = √(21² + 72²) = √(441 + 5184) = √(5625) = 75
Pattern Recognition

Standard algebraic identities recursively applied. Extract sum and product, then ladder up to higher powers.

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Class 11 Maths: Complex Numbers and Quadratic Equations

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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
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