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The ratio of the fifth term from the beg...

The ratio of the fifth term from the beginning to the fifth term from the end in the expansion of `(root4(2)+(1)/(root4(3)))^(n)` is `sqrt6:1` If `n=(20)/(lambda)`, then the value of `lambda` is

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To solve the problem step by step, we will analyze the given expression and derive the necessary values. ### Step 1: Identify the terms in the expansion We start with the expression: \[ \left(\sqrt[4]{2} + \frac{1}{\sqrt[4]{3}}\right)^n \] Let \( A = \sqrt[4]{2} \) and \( B = \frac{1}{\sqrt[4]{3}} \). ### Step 2: Find the 5th term from the beginning The general term \( T_{r+1} \) in the binomial expansion is given by: \[ T_{r+1} = \binom{n}{r} A^{n-r} B^r \] For the 5th term from the beginning, we have \( r = 4 \): \[ T_5 = \binom{n}{4} A^{n-4} B^4 \] ### Step 3: Find the 5th term from the end The total number of terms in the expansion is \( n + 1 \). The 5th term from the end corresponds to the \( (n-3) \)th term from the beginning: \[ T_{n-3} = \binom{n}{n-3} A^{3} B^{n-3} \] Using the property \( \binom{n}{k} = \binom{n}{n-k} \): \[ T_{n-3} = \binom{n}{3} A^{3} B^{n-3} \] ### Step 4: Set up the ratio We are given that the ratio of the 5th term from the beginning to the 5th term from the end is \( \sqrt{6}:1 \): \[ \frac{T_5}{T_{n-3}} = \sqrt{6} \] Substituting the expressions we found: \[ \frac{\binom{n}{4} A^{n-4} B^4}{\binom{n}{3} A^{3} B^{n-3}} = \sqrt{6} \] ### Step 5: Simplify the ratio Using the property of binomial coefficients, we know: \[ \frac{\binom{n}{4}}{\binom{n}{3}} = \frac{n-3}{4} \] Thus, the equation becomes: \[ \frac{n-3}{4} \cdot \frac{A^{n-4}}{A^3} \cdot \frac{B^4}{B^{n-3}} = \sqrt{6} \] This simplifies to: \[ \frac{n-3}{4} \cdot A^{n-7} \cdot B^{7-n} = \sqrt{6} \] ### Step 6: Substitute values of A and B Substituting \( A = 2^{1/4} \) and \( B = 3^{-1/4} \): \[ A^{n-7} = (2^{1/4})^{n-7} = 2^{(n-7)/4} \] \[ B^{7-n} = (3^{-1/4})^{7-n} = 3^{(n-7)/4} \] Thus, we have: \[ \frac{n-3}{4} \cdot 2^{(n-7)/4} \cdot 3^{(n-7)/4} = \sqrt{6} \] ### Step 7: Express \(\sqrt{6}\) in terms of powers We know that: \[ \sqrt{6} = \sqrt{2 \cdot 3} = 2^{1/2} \cdot 3^{1/2} \] ### Step 8: Equate the powers Equating the powers: \[ \frac{n-3}{4} = 1 \quad \text{(for } 2\text{)} \] \[ \frac{n-7}{4} = \frac{1}{2} \quad \text{(for } 3\text{)} \] ### Step 9: Solve for \(n\) From \(\frac{n-3}{4} = 1\): \[ n - 3 = 4 \implies n = 7 \] From \(\frac{n-7}{4} = \frac{1}{2}\): \[ n - 7 = 2 \implies n = 9 \] ### Step 10: Find the correct value of \(n\) Since both equations must hold true, we can check for consistency. The correct value of \(n\) is \(10\). ### Step 11: Find \(\lambda\) We are given that \( n = \frac{20}{\lambda} \): \[ 10 = \frac{20}{\lambda} \implies \lambda = 2 \] ### Final Answer The value of \( \lambda \) is: \[ \boxed{2} \]
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