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Let r,s and t be the roots of the equati...

Let `r,s` and `t` be the roots of the equation `8x^(3)+1001x+2008=0`. If `99lamda=(r+s)^(3)+(s+t)^(3)+(t+r)^(3)`, the value of `[lamda]` (where [.] denotes the greatest integer function) is ____

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To solve the problem step by step, we will analyze the given polynomial equation and apply Vieta's formulas to find the required value of \(\lambda\). ### Step 1: Identify the roots and apply Vieta's formulas The given polynomial is: \[ 8x^3 + 1001x + 2008 = 0 \] Let the roots be \(r\), \(s\), and \(t\). According to Vieta's formulas: - The sum of the roots \(r + s + t = -\frac{\text{coefficient of } x^2}{\text{coefficient of } x^3} = 0\) - The sum of the products of the roots taken two at a time \(rs + rt + st = \frac{\text{coefficient of } x}{\text{coefficient of } x^3} = \frac{1001}{8}\) - The product of the roots \(rst = -\frac{\text{constant term}}{\text{coefficient of } x^3} = -\frac{2008}{8} = -251\) ### Step 2: Define new variables for sums of pairs of roots Let: \[ a = r + s, \quad b = s + t, \quad c = t + r \] From the first step, we know: \[ a + b + c = (r + s) + (s + t) + (t + r) = 2(r + s + t) = 0 \] ### Step 3: Use the identity for the sum of cubes We use the identity: \[ a^3 + b^3 + c^3 - 3abc = (a + b + c)(a^2 + b^2 + c^2 - ab - ac - bc) \] Since \(a + b + c = 0\), we have: \[ a^3 + b^3 + c^3 = 3abc \] ### Step 4: Calculate \(abc\) We know: \[ abc = (r+s)(s+t)(t+r) \] Expanding this: \[ abc = (r+s)(s+t)(t+r) = (r+s+t)(rs + rt + st) - rst \] Since \(r+s+t = 0\), this simplifies to: \[ abc = -rst = 251 \] ### Step 5: Calculate \(a^3 + b^3 + c^3\) Thus: \[ a^3 + b^3 + c^3 = 3abc = 3 \times 251 = 753 \] ### Step 6: Relate to \(\lambda\) We are given: \[ 99\lambda = a^3 + b^3 + c^3 = 753 \] Therefore: \[ \lambda = \frac{753}{99} \] ### Step 7: Simplify \(\lambda\) Calculating \(\frac{753}{99}\): \[ \lambda = 7.60606060606\ldots \] ### Step 8: Apply the greatest integer function The greatest integer function \([\lambda]\) gives us: \[ [\lambda] = 7 \] ### Final Answer The value of \([\lambda]\) is: \[ \boxed{7} \]

To solve the problem step by step, we will analyze the given polynomial equation and apply Vieta's formulas to find the required value of \(\lambda\). ### Step 1: Identify the roots and apply Vieta's formulas The given polynomial is: \[ 8x^3 + 1001x + 2008 = 0 \] Let the roots be \(r\), \(s\), and \(t\). According to Vieta's formulas: ...
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