If 1, ๐,๐2 are cube roots of unity, show that(2 โ ๐) (2 โ ๐2) (2 โ ๐19) (2 โ ๐23) = 49.
Question
If 1, ๐,๐2 are cube roots of unity, show that(2 โ ๐) (2 โ ๐2) (2 โ ๐19) (2 โ ๐23) = 49.
Solution
Sure, let's solve this step by step.
Step 1: We know that the cube roots of unity are 1, ๐, ๐ยฒ. These are the roots of the equation xยณ = 1.
Step 2: We also know that ๐ยณ = 1, so ๐โด = ๐, ๐โต = ๐ยฒ, ๐โถ = 1, and so on. This means that we can express ๐ยนโน and ๐ยฒยณ in terms of ๐ and ๐ยฒ.
Step 3: ๐ยนโน = ๐โถ3 + 1 = ๐ยน = ๐ and ๐ยฒยณ = ๐โถ3 + 2 = ๐ยฒ.
Step 4: Now we substitute ๐ยนโน and ๐ยฒยณ in the given expression with ๐ and ๐ยฒ respectively. So, (2 โ ๐) (2 โ ๐ยฒ) (2 โ ๐ยนโน) (2 โ ๐ยฒยณ) becomes (2 โ ๐) (2 โ ๐ยฒ) (2 โ ๐) (2 โ ๐ยฒ).
Step 5: This simplifies to [(2 โ ๐)ยฒ] [(2 โ ๐ยฒ)ยฒ].
Step 6: We know that 1 + ๐ + ๐ยฒ = 0, so ๐ยฒ = -1 - ๐ and ๐ = -1 - ๐ยฒ.
Step 7: Substituting these values in, we get [(2 โ (-1 - ๐ยฒ))ยฒ] [(2 โ (-1 - ๐))ยฒ] = (3 + ๐ยฒ)ยฒ (3 + ๐)ยฒ.
Step 8: Expanding this, we get (9 + 6๐ยฒ + ๐โด) (9 + 6๐ + ๐ยฒ).
Step 9: Substituting ๐โด = ๐ and ๐ยฒ = -1 - ๐, we get (9 + 6(-1 - ๐) + ๐) (9 + 6๐ - 1 - ๐).
Step 10: Simplifying this, we get (8 - 5๐) (8 + 5๐).
Step 11: Finally, multiplying this out, we get 64 - 25๐ยฒ.
Step 12: Substituting ๐ยฒ = -1 - ๐, we get 64 - 25(-1 - ๐) = 64 + 25 + 25๐ = 89 + 25๐.
Step 13: But we know that ๐ + 1 = -๐ยฒ, so 89 + 25๐ = 89 - 25๐ยฒ = 89 - 25(-1 - ๐) = 89 + 25 + 25๐ = 114 + 25๐.
Step 14: Repeating this process, we get 114 + 25(-1 - ๐) = 114 - 25 - 25๐ = 89 - 25๐.
Step 15: This process will continue indefinitely, so the expression does not simplify to a constant value. Therefore, the given statement is not true. The expression (2 โ ๐) (2 โ ๐ยฒ) (2 โ ๐ยนโน) (2 โ ๐ยฒยณ) does not equal 49.
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