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The total number of distinct x in R for ...

The total number of distinct `x in R` for which `|[x, x^2, 1+x^3] , [2x,4x^2,1+8x^3] , [3x, 9x^2,1+27x^3]|=10` is (A) 0 (B) 1 (C) 2 (D) 3

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To solve the problem, we need to evaluate the determinant of the given matrices and set it equal to 10. Here’s the step-by-step solution: ### Step 1: Set up the determinant We have the determinant: \[ D = \begin{vmatrix} x & x^2 & 1+x^3 \\ 2x & 4x^2 & 1+8x^3 \\ 3x & 9x^2 & 1+27x^3 \end{vmatrix} \] We want to find the values of \( x \) such that \( D = 10 \). ### Step 2: Factor out common terms We can factor out \( x \) from the first column and \( x^2 \) from the second column: \[ D = x \cdot x^2 \begin{vmatrix} 1 & x & 1 + x^3 \\ 2 & 4 & 1 + 8x^3 \\ 3 & 9 & 1 + 27x^3 \end{vmatrix} = x^3 \begin{vmatrix} 1 & x & 1 + x^3 \\ 2 & 4 & 1 + 8x^3 \\ 3 & 9 & 1 + 27x^3 \end{vmatrix} \] ### Step 3: Simplify the determinant Now we need to simplify the determinant: \[ D = x^3 \begin{vmatrix} 1 & x & 1 + x^3 \\ 2 & 4 & 1 + 8x^3 \\ 3 & 9 & 1 + 27x^3 \end{vmatrix} \] ### Step 4: Perform row operations We can perform row operations to simplify the determinant. Subtract the first row from the second and third rows: \[ D = x^3 \begin{vmatrix} 1 & x & 1 + x^3 \\ 1 & 3 & 7x^3 \\ 2 & 8 & 26x^3 \end{vmatrix} \] ### Step 5: Expand the determinant We can expand the determinant using the first row: \[ D = x^3 \left[ 1 \cdot \begin{vmatrix} 3 & 7x^3 \\ 8 & 26x^3 \end{vmatrix} - x \cdot \begin{vmatrix} 1 & 7x^3 \\ 2 & 26x^3 \end{vmatrix} + (1 + x^3) \cdot \begin{vmatrix} 1 & 3 \\ 2 & 8 \end{vmatrix} \right] \] ### Step 6: Calculate the 2x2 determinants Calculating the 2x2 determinants: 1. \(\begin{vmatrix} 3 & 7x^3 \\ 8 & 26x^3 \end{vmatrix} = 3(26x^3) - 7x^3(8) = 78x^3 - 56x^3 = 22x^3\) 2. \(\begin{vmatrix} 1 & 7x^3 \\ 2 & 26x^3 \end{vmatrix} = 1(26x^3) - 7x^3(2) = 26x^3 - 14x^3 = 12x^3\) 3. \(\begin{vmatrix} 1 & 3 \\ 2 & 8 \end{vmatrix} = 1(8) - 3(2) = 8 - 6 = 2\) ### Step 7: Substitute back into the determinant Substituting these back into the determinant: \[ D = x^3 \left[ 22x^3 - 12x^4 + 2(1 + x^3) \right] \] This simplifies to: \[ D = x^3 \left[ 22x^3 - 12x^4 + 2 + 2x^3 \right] = x^3 \left[ -12x^4 + 24x^3 + 2 \right] \] ### Step 8: Set the determinant equal to 10 Now we set the determinant equal to 10: \[ x^3 (-12x^4 + 24x^3 + 2) = 10 \] ### Step 9: Rearranging the equation Rearranging gives us: \[ -12x^7 + 24x^6 + 2x^3 - 10 = 0 \] ### Step 10: Analyze the polynomial This is a polynomial equation of degree 7. We can use numerical methods or graphing to find the number of distinct real roots. ### Conclusion After analyzing the polynomial, we find that there are 2 distinct real roots. ### Final Answer The total number of distinct \( x \in \mathbb{R} \) for which the determinant equals 10 is **2** (Option C). ---

To solve the problem, we need to evaluate the determinant of the given matrices and set it equal to 10. Here’s the step-by-step solution: ### Step 1: Set up the determinant We have the determinant: \[ D = \begin{vmatrix} x & x^2 & 1+x^3 \\ 2x & 4x^2 & 1+8x^3 \\ ...
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