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Let X=(\ ^(10)C1)^2+2(\ ^(10)C2)^2+3(\ ^...

Let `X=(\ ^(10)C_1)^2+2(\ ^(10)C_2)^2+3(\ ^(10)C_3)^2+\ ddot\ +10(\ ^(10)C_(10))^2` , where `\ ^(10)C_r` , `r in {1,\ 2,\ ddot,\ 10}` denote binomial coefficients. Then, the value of `1/(1430)\ X` is _________.

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To solve the problem, we need to evaluate the expression: \[ X = \sum_{r=1}^{10} r \cdot \binom{10}{r}^2 \] ### Step 1: Use the Identity for Binomial Coefficients We can use the identity that relates the sum of products of binomial coefficients: \[ \sum_{r=0}^{n} r \cdot \binom{n}{r} = n \cdot 2^{n-1} \] This means we can express our sum in terms of binomial coefficients. ### Step 2: Rewrite the Expression We can rewrite \(X\) as follows: \[ X = \sum_{r=1}^{10} r \cdot \binom{10}{r}^2 = \sum_{r=1}^{10} r \cdot \binom{10}{r} \cdot \binom{10}{r} \] ### Step 3: Apply the Identity Using the identity mentioned earlier, we can find that: \[ \sum_{r=1}^{10} r \cdot \binom{10}{r}^2 = 10 \cdot \sum_{r=1}^{10} \binom{10-1}{r-1} \cdot \binom{10}{r} \] ### Step 4: Use Vandermonde's Identity By applying Vandermonde's identity, we can simplify: \[ \sum_{r=0}^{n} \binom{m}{r} \cdot \binom{n}{k-r} = \binom{m+n}{k} \] In our case, we have \(m = n = 10\) and \(k = 10\): \[ \sum_{r=0}^{10} \binom{10}{r} \cdot \binom{10}{10-r} = \binom{20}{10} \] ### Step 5: Calculate \(X\) Thus, we can express \(X\) as: \[ X = 10 \cdot \binom{20}{10} \] ### Step 6: Calculate \(\binom{20}{10}\) Now we need to calculate \(\binom{20}{10}\): \[ \binom{20}{10} = \frac{20!}{10! \cdot 10!} = 184756 \] ### Step 7: Substitute Back into \(X\) Now substituting back into our expression for \(X\): \[ X = 10 \cdot 184756 = 1847560 \] ### Step 8: Find \(\frac{X}{1430}\) Finally, we need to compute: \[ \frac{X}{1430} = \frac{1847560}{1430} \] Calculating this gives: \[ \frac{1847560}{1430} = 12920 \] ### Final Answer Thus, the value of \(\frac{X}{1430}\) is: \[ \boxed{12920} \]

To solve the problem, we need to evaluate the expression: \[ X = \sum_{r=1}^{10} r \cdot \binom{10}{r}^2 \] ### Step 1: Use the Identity for Binomial Coefficients We can use the identity that relates the sum of products of binomial coefficients: ...
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