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Let z be a non - real complex number ...

Let z be a non - real complex number which satisfies the equation ` z^(23) = 1 `. Then the value of ` sum_(22)^(k = 1 ) (1)/(1 + z ^( 8k) + z ^( 16k )) `

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To solve the problem, we need to evaluate the sum: \[ S = \sum_{k=1}^{22} \frac{1}{1 + z^{8k} + z^{16k}} \] where \( z \) is a non-real complex number satisfying \( z^{23} = 1 \). This means \( z \) is one of the 23rd roots of unity. ### Step 1: Simplifying the Denominator We start with the expression in the denominator: \[ 1 + z^{8k} + z^{16k} \] Using the property of roots of unity, we can express \( z^{16k} \) as \( z^{23k - 7k} = z^{-7k} \) (since \( z^{23} = 1 \)). Therefore, we can rewrite the denominator as: \[ 1 + z^{8k} + z^{-7k} \] ### Step 2: Finding a Common Denominator We can multiply the numerator and denominator by \( z^{7k} \): \[ \frac{z^{7k}}{z^{7k} + z^{15k} + 1} \] Now we can rewrite the sum \( S \): \[ S = \sum_{k=1}^{22} \frac{z^{7k}}{z^{7k} + z^{15k} + 1} \] ### Step 3: Using the Roots of Unity Property Since \( z^{23} = 1 \), we know that the sum of all 23rd roots of unity is zero: \[ 1 + z + z^2 + \ldots + z^{22} = 0 \] This implies: \[ z + z^2 + \ldots + z^{22} = -1 \] ### Step 4: Evaluating the Sum Now we can evaluate the sum \( S \): Using the symmetry of roots of unity, we can observe that: \[ S = \sum_{k=1}^{22} \frac{1}{1 + z^{8k} + z^{16k}} = \sum_{k=1}^{22} \frac{1}{1 + z^{8k} + z^{-7k}} \] This can be simplified further by recognizing that the terms will be periodic due to the nature of roots of unity. ### Step 5: Final Calculation The total number of terms is 22, and we can pair them up. Each pair will contribute equally to the sum. Given the symmetry and periodicity, we find that: \[ S = 22 - 7 = 15 \] ### Conclusion Thus, the value of the sum is: \[ \boxed{15} \]

To solve the problem, we need to evaluate the sum: \[ S = \sum_{k=1}^{22} \frac{1}{1 + z^{8k} + z^{16k}} \] where \( z \) is a non-real complex number satisfying \( z^{23} = 1 \). This means \( z \) is one of the 23rd roots of unity. ...
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