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If the number of terms free from radical...

If the number of terms free from radicals in the expansion of `(7^((1)/(3))+11^((1)/(9)))^(6561)` is k, then the value of `(k)/(100)` is equal to

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To solve the problem, we need to find the number of terms free from radicals in the expansion of \((7^{\frac{1}{3}} + 11^{\frac{1}{9}})^{6561}\). ### Step-by-Step Solution: 1. **Identify the General Term**: The general term \(T_{r+1}\) in the binomial expansion of \((a + b)^n\) is given by: \[ T_{r+1} = \binom{n}{r} a^{n-r} b^r \] For our expression, \(a = 7^{\frac{1}{3}}\), \(b = 11^{\frac{1}{9}}\), and \(n = 6561\). Thus, the general term becomes: \[ T_{r+1} = \binom{6561}{r} (7^{\frac{1}{3}})^{6561 - r} (11^{\frac{1}{9}})^{r} \] Simplifying this gives: \[ T_{r+1} = \binom{6561}{r} 7^{\frac{6561 - r}{3}} 11^{\frac{r}{9}} \] 2. **Condition for Rational Terms**: We want the term to be free from radicals, which means both exponents must be integers. Therefore, we need: - \(\frac{6561 - r}{3}\) to be an integer, which implies \(6561 - r \equiv 0 \mod 3\) - \(\frac{r}{9}\) to be an integer, which implies \(r \equiv 0 \mod 9\) 3. **Finding Valid Values for \(r\)**: From \(r \equiv 0 \mod 9\), we can write \(r = 9k\) for some integer \(k\). The maximum value of \(r\) is \(6561\), so: \[ 9k \leq 6561 \implies k \leq \frac{6561}{9} = 729 \] Therefore, \(k\) can take values from \(0\) to \(729\). 4. **Counting Valid \(k\) Values**: The possible values of \(k\) are \(0, 1, 2, \ldots, 729\). This gives us a total of: \[ 729 - 0 + 1 = 730 \text{ values} \] 5. **Finding \(k/100\)**: Since the number of terms free from radicals is \(k = 730\), we need to find: \[ \frac{k}{100} = \frac{730}{100} = 7.3 \] ### Final Answer: Thus, the value of \(\frac{k}{100}\) is \(7.3\).
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