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If p + q + r = a + b + c = 0, then the d...

If p + q + r = a + b + c = 0, then the determinant `|{:(pa,qb,rc),(qc,ra,pb),(rb,pc,qa):}|` equals

A

0

B

1

C

pa + qb + rc

D

pa + qb + rc + a + b + c

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To solve the determinant \( D = \begin{vmatrix} pa & qb & rc \\ qc & ra & pb \\ rb & pc & qa \end{vmatrix} \) given that \( p + q + r = 0 \) and \( a + b + c = 0 \), we can follow these steps: ### Step 1: Write the Determinant We start with the determinant: \[ D = \begin{vmatrix} pa & qb & rc \\ qc & ra & pb \\ rb & pc & qa \end{vmatrix} \] ### Step 2: Expand the Determinant We can expand the determinant using the first row: \[ D = pa \begin{vmatrix} ra & pb \\ pc & qa \end{vmatrix} - qb \begin{vmatrix} qc & pb \\ rb & qa \end{vmatrix} + rc \begin{vmatrix} qc & ra \\ rb & pc \end{vmatrix} \] ### Step 3: Calculate the 2x2 Determinants Now we calculate the 2x2 determinants one by one. 1. For \( \begin{vmatrix} ra & pb \\ pc & qa \end{vmatrix} \): \[ = (ra)(qa) - (pb)(pc) = raqa - pbpc \] 2. For \( \begin{vmatrix} qc & pb \\ rb & qa \end{vmatrix} \): \[ = (qc)(qa) - (pb)(rb) = qcqa - pbrb \] 3. For \( \begin{vmatrix} qc & ra \\ rb & pc \end{vmatrix} \): \[ = (qc)(pc) - (ra)(rb) = qcpc - rarb \] ### Step 4: Substitute Back into the Determinant Now substitute these back into the expression for \( D \): \[ D = pa(raqa - pbpc) - qb(qcqa - pbrb) + rc(qcpc - rarb) \] ### Step 5: Simplify the Expression Now we simplify the expression: \[ D = paraqa - papbpc - qbqcqa + qbpbrb + rcqcpc - rcarb \] ### Step 6: Use the Given Conditions Using the conditions \( p + q + r = 0 \) and \( a + b + c = 0 \), we can 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: \[ a^3 + b^3 + c^3 = 3abc \] Similarly, we can apply this to \( p, q, r \): \[ p^3 + q^3 + r^3 = 3pqr \] ### Step 7: Final Result Substituting these identities into our expression for \( D \): \[ D = pqr(3abc) - abc(3pqr) = 3pqrabc - 3pqrabc = 0 \] Thus, the value of the determinant is: \[ \boxed{0} \]

To solve the determinant \( D = \begin{vmatrix} pa & qb & rc \\ qc & ra & pb \\ rb & pc & qa \end{vmatrix} \) given that \( p + q + r = 0 \) and \( a + b + c = 0 \), we can follow these steps: ### Step 1: Write the Determinant We start with the determinant: \[ D = \begin{vmatrix} pa & qb & rc \\ qc & ra & pb \\ rb & pc & qa \end{vmatrix} \] ...
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NDA PREVIOUS YEARS-MATRICES & DETERMINANTS-MQS
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