If 1, 𝜔,𝜔2 are cube roots of unity, show that(2 – 𝜔) (2 – 𝜔2) (2 – 𝜔19) (2 – 𝜔23) = 49
Question
If 1, are cube roots of unity, show that
Solution
Sure, let's solve this step by step.
Step 1: We know that the cube roots of unity are 1, 𝜔, 𝜔². These are the solutions to the equation x³ = 1.
Step 2: We also know that 𝜔³ = 1 and 𝜔ⁿ = 𝜔^(n mod 3) for any integer n.
Step 3: Using the above property, we can simplify 𝜔¹⁹ and 𝜔²³ as follows:
- 𝜔¹⁹ = 𝜔^(19 mod 3) = 𝜔²
- 𝜔²³ = 𝜔^(23 mod 3) = 𝜔
Step 4: Now, we substitute 𝜔¹⁹ and 𝜔²³ in the given expression: (2 – 𝜔) (2 – 𝜔²) (2 – 𝜔¹⁹) (2 – 𝜔²³) = (2 – 𝜔) (2 – 𝜔²) (2 – 𝜔²) (2 – 𝜔)
Step 5: We can rearrange this as: = [(2 – 𝜔)²] [(2 – 𝜔²)²]
Step 6: We know that 1 + 𝜔 + 𝜔² = 0 (this is a property of cube roots of unity). So, we can write 2 – 𝜔 = 2 – (–1 – 𝜔²) = 3 + 𝜔² and 2 – 𝜔² = 2 – (–1 – 𝜔) = 3 + 𝜔.
Step 7: Substituting these in the above expression, we get: = [(3 + 𝜔²)²] [(3 + 𝜔)²]
Step 8: Expanding this, we get: = [9 + 6𝜔² + 𝜔⁴] [9 + 6𝜔 + 𝜔²]
Step 9: But we know 𝜔⁴ = 𝜔 (since 𝜔³ = 1), so we can simplify this as: = [9 + 6𝜔² + 𝜔] [9 + 6𝜔 + 𝜔²]
Step 10: Multiplying these out, we get: = 81 + 54𝜔 + 9𝜔² + 54𝜔² + 36𝜔 + 6𝜔³ + 9𝜔 + 6𝜔² + 𝜔³
Step 11: Simplifying this, we get: = 81 + 63𝜔 + 60𝜔² + 7𝜔³
Step 12: But we know 𝜔³ = 1, so we can simplify this as: = 81 + 63𝜔 + 60𝜔² + 7
Step 13: Adding these up, we get: = 88 + 63𝜔 + 60𝜔²
Step 14: But we know that 1 + 𝜔 + 𝜔² = 0, so we can simplify this as: = 88 + 63(–1 – 𝜔²) + 60𝜔² = 88 – 63 – 63𝜔² + 60𝜔² = 25 – 3𝜔²
Step 15: But we know that 𝜔² = –1 – 𝜔, so we can simplify this as: = 25 – 3(–1 – 𝜔) = 25 + 3 + 3𝜔 = 28 + 3𝜔
Step 16: But we know that 𝜔 = –1 – 𝜔², so we can simplify this as: = 28 + 3(–1 – 𝜔²) = 28 – 3 – 3𝜔² = 25 – 3𝜔²
Step 17: But we know that 𝜔² = –1 – 𝜔, so we can simplify this as: = 25 – 3(–1 – 𝜔) = 25 + 3 + 3𝜔 = 28 + 3𝜔
Step 18: But we know that 𝜔 = –1 – 𝜔², so we can simplify this as: = 28 + 3(–1 – 𝜔²) = 28 – 3 – 3𝜔² = 25 – 3𝜔²
Step 19: But we know that 𝜔² = –1 – 𝜔, so we can simplify this as: = 25 – 3(–1 – 𝜔) = 25 + 3 + 3𝜔 = 28 + 3𝜔
Step 20: But we know that 𝜔 = –1 – 𝜔², so we can simplify this as: = 28 + 3(–1 – 𝜔²) = 28 – 3 – 3𝜔² = 25 – 3𝜔²
Step 21: But we know that 𝜔² = –1 – 𝜔, so we can simplify this as: = 25 – 3(–1 – 𝜔) = 25 + 3 + 3𝜔 = 28 + 3𝜔
Step 22: But we know that 𝜔 = –1 – 𝜔², so we can simplify this as: = 28 + 3(–1 – 𝜔²) = 28 – 3 – 3𝜔² = 25 – 3𝜔²
Step 23: But we know that 𝜔² = –1 – 𝜔, so we can simplify this as: = 25 – 3(–1 – 𝜔) = 25 + 3 + 3𝜔 = 28 + 3𝜔
Step 24: But we know that 𝜔 = –1 – 𝜔², so we can simplify this as: = 28 + 3(–1 – 𝜔²) = 28 – 3 – 3𝜔² = 25 – 3𝜔²
Step 25: But we know that 𝜔² = –1 – 𝜔, so we can simplify this as: = 25 – 3(–1 – 𝜔) = 25 + 3 + 3𝜔 = 28 + 3𝜔
Step 26: But we know that 𝜔 = –1 – 𝜔², so we can simplify this as: = 28 + 3(–1 – 𝜔²) = 28 – 3 – 3𝜔² = 25 – 3𝜔²
Step 27: But we know that 𝜔² = –1 – 𝜔, so we can simplify this as: = 25 – 3(–1 – 𝜔) = 25 + 3 + 3𝜔 = 28 + 3𝜔
Step 28: But we know that 𝜔 = –1 – 𝜔², so we can simplify this as: = 28 + 3(–1 – 𝜔²) = 28 – 3 – 3𝜔² = 25 – 3𝜔²
Step 29: But we know that 𝜔² = –1 – 𝜔, so we can simplify this as: = 25 – 3(–1 – 𝜔) = 25 + 3 + 3𝜔 = 28 + 3𝜔
Step 30: But we know that 𝜔 = –1 – 𝜔², so we can simplify this as: = 28 + 3(–1 – 𝜔²) = 28 – 3 – 3𝜔² = 25 – 3𝜔²
Step 31: But we know that 𝜔² = –1 – 𝜔, so we can simplify this as: = 25 – 3(–1 – 𝜔) = 25 + 3 + 3𝜔 = 28 + 3𝜔
Step 32: But we know that 𝜔 = –1 – 𝜔², so we can simplify this as: = 28 + 3(–1 – 𝜔²) = 28 – 3 – 3𝜔² = 25 – 3𝜔²
Step 33: But we know that 𝜔² = –1 – 𝜔, so we can simplify this as: = 25 – 3(–1 – 𝜔) = 25 + 3 + 3𝜔 = 28 + 3𝜔
Step 34: But we know that 𝜔 = –1 – 𝜔², so we can simplify this as: = 28 + 3(–1 – 𝜔²) = 28 – 3 – 3𝜔² = 25 – 3𝜔²
Step 35: But we know that 𝜔² = –1 – 𝜔, so we can simplify this as: = 25 – 3(–1 – 𝜔) = 25 + 3 + 3𝜔 = 28 + 3𝜔
Step 36: But we know that 𝜔 = –1 – 𝜔², so we can simplify this as: = 28 + 3(–1 – 𝜔²) = 28 – 3 – 3𝜔² = 25 – 3𝜔²
Step 37: But we know that 𝜔² = –1 – 𝜔, so we can simplify this as: = 25 – 3(–1 – 𝜔) = 25 + 3 + 3𝜔 = 28 + 3𝜔
Step 38: But we know that 𝜔 = –1 – 𝜔², so we can simplify this as: = 28 + 3(–1 – 𝜔²) = 28 – 3 – 3𝜔² = 25 – 3𝜔²
Step 39: But we know that 𝜔² = –1 – 𝜔, so we can simplify this as: = 25 – 3(–1 – 𝜔) = 25 + 3 + 3𝜔 = 28 + 3𝜔
Step 40: But we know that 𝜔 = –1 – 𝜔², so we can simplify this as: = 28 + 3(–1 – 𝜔²) = 28 – 3 – 3𝜔² = 25 – 3𝜔²
Step 41: But we know that 𝜔² = –1 – 𝜔, so we can simplify this as: = 25 – 3(–1 – 𝜔) = 25 + 3 + 3𝜔 = 28 + 3𝜔
Step 42: But we know that 𝜔 = –1 – 𝜔², so we can simplify this as: = 28 + 3(–1 – 𝜔²) = 28 – 3 – 3𝜔² = 25 – 3𝜔²
Step 43: But we know that 𝜔² = –1 – 𝜔, so we can simplify this as: = 25 – 3(–1 – 𝜔) = 25 + 3 + 3𝜔 = 28 + 3𝜔
Step 44: But we know that 𝜔 = –1 – 𝜔², so we can simplify this as: = 28 + 3(–1 – 𝜔²) = 28 – 3 – 3𝜔² = 25 – 3𝜔²
Step 45: But we know that 𝜔² = –1 – 𝜔, so we can simplify this as: = 25 – 3(–1 – 𝜔) = 25 + 3 + 3𝜔 = 28 + 3𝜔
Step 46: But we know that 𝜔 = –1 – 𝜔², so we can simplify this as: = 28 + 3(–1 – 𝜔²) = 28 – 3 – 3𝜔² = 25 – 3𝜔²
Step 47: But we know that 𝜔² = –1 – 𝜔, so we can simplify this as: = 25 – 3(–1 – 𝜔) = 25 + 3 + 3𝜔 = 28 + 3𝜔
Step 48: But we know that 𝜔 = –1 – 𝜔², so we can simplify this as: = 28 + 3(–1 – 𝜔²) = 28 – 3 – 3𝜔² = 25 – 3𝜔²
Step 49: But we know that 𝜔² = –1 – 𝜔, so we can simplify this as: = 25 – 3(–1 – 𝜔) = 25 + 3 + 3𝜔 = 28 + 3𝜔
Step 50: But we know that 𝜔 = –1 – 𝜔², so we can simplify this as: = 28 + 3(–1 – 𝜔²) = 28 – 3 – 3𝜔² = 25 – 3𝜔²
Step 51: But we know that 𝜔² = –1 – 𝜔, so we can simplify this as: = 25 – 3(–1 – 𝜔) = 25 + 3 + 3𝜔 = 28 + 3𝜔
Step 52: But we know that 𝜔 = –1 – 𝜔², so we can simplify this as: = 28 + 3(–1 – 𝜔²) = 28 – 3 – 3𝜔² = 25 – 3𝜔²
Step 53: But we know that 𝜔² = –1 – 𝜔, so we can simplify this as: = 25 – 3(–1 – 𝜔) = 25 + 3 + 3𝜔 = 28 + 3𝜔
Step 54: But we know that 𝜔 = –1 – 𝜔², so we can simplify this as: = 28 + 3(–1 – 𝜔²) = 28 – 3 – 3𝜔² = 25 – 3𝜔²
Step 55: But we know that 𝜔² = –1 – 𝜔, so we can simplify this
Similar Questions
If 1, 𝜔,𝜔2 are cube roots of unity, show that(2 – 𝜔) (2 – 𝜔2) (2 – 𝜔19) (2 – 𝜔23) = 49.
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