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The value of ∣1bcbc(b+c)1caca(c+a)1abab(a+b)∣\begin{vmatrix} 1 & bc & bc(b+c) \\ 1 & ca & ca(c+a) \\ 1 & ab & ab(a+b) \end{vmatrix} is

Solution

✅ Correct Option: 2

∣1bcbc(b+c)1caca(c+a)1abab(a+b)∣\begin{vmatrix} 1 & bc & bc(b+c) \\ 1 & ca & ca(c+a) \\ 1 & ab & ab(a+b) \end{vmatrix}


Applying R2→R2−R1R_2 \to R_2 - R_1 and R3→R3−R1R_3 \to R_3 - R_1:

=∣1bcbc(b+c)0ca−bcca(c+a)−bc(b+c)0ab−bcab(a+b)−bc(b+c)∣= \begin{vmatrix} 1 & bc & bc(b+c) \\ 0 & ca - bc & ca(c+a) - bc(b+c) \\ 0 & ab - bc & ab(a+b) - bc(b+c) \end{vmatrix}


For R2R_2:

ca−bc=c(a−b)ca - bc = c(a - b)

ca(c+a)−bc(b+c)ca(c+a) - bc(b+c)

=c(a2+ac−b2−bc)= c(a^2 + ac - b^2 - bc)

=c[(a2−b2)+c(a−b)]= c[(a^2 - b^2) + c(a - b)]

=c(a−b)(a+b+c)= c(a-b)(a+b+c)

For R3R_3:

ab−bc=b(a−c)ab - bc = b(a - c)

ab(a+b)−bc(b+c)ab(a+b) - bc(b+c)

=b(a2+ab−c2−bc)= b(a^2 + ab - c^2 - bc)

=b[(a2−c2)+b(a−c)]= b[(a^2 - c^2) + b(a - c)]

=b(a−c)(a+b+c)= b(a-c)(a+b+c)


=∣1bcbc(b+c)0c(a−b)c(a−b)(a+b+c)0b(a−c)b(a−c)(a+b+c)∣= \begin{vmatrix} 1 & bc & bc(b+c) \\ 0 & c(a-b) & c(a-b)(a+b+c) \\ 0 & b(a-c) & b(a-c)(a+b+c) \end{vmatrix}


Expanding along C1C_1:

=1×∣c(a−b)c(a−b)(a+b+c)b(a−c)b(a−c)(a+b+c)∣= 1 \times \begin{vmatrix} c(a-b) & c(a-b)(a+b+c) \\ b(a-c) & b(a-c)(a+b+c) \end{vmatrix}

In this 2×22 \times 2 matrix, C2=(a+b+c)×C1C_2 = (a+b+c) \times C_1.

Since two columns are proportional, the determinant equals 0\boxed{0}.

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