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Let Delta=|(a,a^(2),0),(1,2a+b,(a+b)^(2)...

Let `Delta=|(a,a^(2),0),(1,2a+b,(a+b)^(2)),(0,1,2a+3b)|` then

A

`a + b` is a factor of `Delta`

B

`a + 2b` is a factor of `Delta`

C

`2a+3b` is a factor of `Delta`

D

`a^(2)` is a factor of `Delta`

Text Solution

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The correct Answer is:
To solve the determinant \( \Delta = \begin{vmatrix} a & a^2 & 0 \\ 1 & 2a + b & (a + b)^2 \\ 0 & 1 & 2a + 3b \end{vmatrix} \), we will expand it along the first row. ### Step 1: Write the determinant We start with the determinant as given: \[ \Delta = \begin{vmatrix} a & a^2 & 0 \\ 1 & 2a + b & (a + b)^2 \\ 0 & 1 & 2a + 3b \end{vmatrix} \] ### Step 2: Expand along the first row Using the cofactor expansion along the first row, we have: \[ \Delta = a \cdot \begin{vmatrix} 2a + b & (a + b)^2 \\ 1 & 2a + 3b \end{vmatrix} - a^2 \cdot \begin{vmatrix} 1 & (a + b)^2 \\ 0 & 2a + 3b \end{vmatrix} + 0 \] ### Step 3: Calculate the first minor Calculate the first minor: \[ \begin{vmatrix} 2a + b & (a + b)^2 \\ 1 & 2a + 3b \end{vmatrix} = (2a + b)(2a + 3b) - (a + b)^2 \] Expanding this: \[ = (4a^2 + 6ab + 2ab + 3b^2) - (a^2 + 2ab + b^2) = 4a^2 + 8ab + 3b^2 - a^2 - 2ab - b^2 \] \[ = 3a^2 + 6ab + 2b^2 \] ### Step 4: Calculate the second minor Calculate the second minor: \[ \begin{vmatrix} 1 & (a + b)^2 \\ 0 & 2a + 3b \end{vmatrix} = 1 \cdot (2a + 3b) - 0 = 2a + 3b \] ### Step 5: Substitute back into the determinant Now substitute these minors back into the expression for \(\Delta\): \[ \Delta = a(3a^2 + 6ab + 2b^2) - a^2(2a + 3b) \] Expanding this gives: \[ = 3a^3 + 6a^2b + 2ab^2 - (2a^3 + 3a^2b) \] \[ = (3a^3 - 2a^3) + (6a^2b - 3a^2b) + 2ab^2 = a^3 + 3a^2b + 2ab^2 \] ### Step 6: Factor the result We can factor out \(a\) from the expression: \[ \Delta = a(a^2 + 3ab + 2b^2) \] Now we can factor the quadratic: \[ a^2 + 3ab + 2b^2 = (a + b)(a + 2b) \] Thus, we have: \[ \Delta = a(a + b)(a + 2b) \] ### Final Result Therefore, the final expression for the determinant is: \[ \Delta = a(a + b)(a + 2b) \]
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