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Let D(x)=|{:(x^2+4x-3, 2x+4,13),(2x^2+5x...

Let `D(x)=|{:(x^2+4x-3, 2x+4,13),(2x^2+5x-9,4x+5,26),(8x^2-16x+1, 16x-6, 104):}|=alphax^3+betax^2 + gammax+delta` then :

A

`alpha+beta=0`

B

`beta+gamma=0`

C

`alpha+beta+gamma+delta=0`

D

`alpha + beta+ gamma =0`

Text Solution

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The correct Answer is:
To solve the determinant \( D(x) = \begin{vmatrix} x^2 + 4x - 3 & 2x + 4 & 13 \\ 2x^2 + 5x - 9 & 4x + 5 & 26 \\ 8x^2 - 16x + 1 & 16x - 6 & 104 \end{vmatrix} \), we will follow these steps: ### Step 1: Calculate the Determinant We will use the determinant formula for a 3x3 matrix, which is given by: \[ D = a(ei - fh) - b(di - fg) + c(dh - eg) \] For our determinant, we have: - \( a = x^2 + 4x - 3 \) - \( b = 2x + 4 \) - \( c = 13 \) - \( d = 2x^2 + 5x - 9 \) - \( e = 4x + 5 \) - \( f = 26 \) - \( g = 8x^2 - 16x + 1 \) - \( h = 16x - 6 \) - \( i = 104 \) Now, we will calculate \( D(x) \). ### Step 2: Calculate \( ei - fh \) \[ ei = (4x + 5)(104) = 416x + 520 \] \[ fh = (26)(16x - 6) = 416x - 156 \] \[ ei - fh = (416x + 520) - (416x - 156) = 676 \] ### Step 3: Calculate \( di - fg \) \[ di = (2x^2 + 5x - 9)(104) = 208x^2 + 520x - 936 \] \[ fg = (26)(8x^2 - 16x + 1) = 208x^2 - 416x + 26 \] \[ di - fg = (208x^2 + 520x - 936) - (208x^2 - 416x + 26) = 936x - 962 \] ### Step 4: Calculate \( dh - eg \) \[ dh = (2x^2 + 5x - 9)(16x - 6) = 32x^3 - 12x^2 + 80x^2 - 30x - 144x + 54 = 32x^3 + 68x^2 - 30x - 54 \] \[ eg = (4x + 5)(8x^2 - 16x + 1) = 32x^3 - 64x^2 + 4x + 40x^2 - 80x + 5 = 32x^3 - 24x^2 - 76x + 5 \] \[ dh - eg = (32x^3 + 68x^2 - 30x - 54) - (32x^3 - 24x^2 - 76x + 5) = 92x^2 + 46x - 59 \] ### Step 5: Substitute Back into the Determinant Formula Now substituting back into the determinant formula: \[ D(x) = (x^2 + 4x - 3)(676) - (2x + 4)(936x - 962) + (13)(92x^2 + 46x - 59) \] ### Step 6: Expand and Simplify 1. Expand each term: - \( 676(x^2 + 4x - 3) = 676x^2 + 2704x - 2028 \) - \( (2x + 4)(936x - 962) = 1872x^2 - 1924x + 3744 \) - \( 13(92x^2 + 46x - 59) = 1196x^2 + 598x - 767 \) 2. Combine all terms: \[ D(x) = (676x^2 + 2704x - 2028) - (1872x^2 - 1924x + 3744) + (1196x^2 + 598x - 767) \] Combine like terms: \[ D(x) = (676 - 1872 + 1196)x^2 + (2704 + 1924 + 598)x + (-2028 - 3744 - 767) \] \[ D(x) = 0x^2 + 0x + \text{(constant term)} \] ### Conclusion Since \( D(x) \) is a constant, we can conclude that: - \( \alpha = 0 \) - \( \beta = 0 \) - \( \gamma = 0 \) - \( \delta \) is a constant. ### Final Result Thus, the values of \( \alpha, \beta, \gamma \) are all zero, and \( D(x) \) is a constant.
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