Question:medium

If \( A = \begin{vmatrix} 1 & a & a^2 \\ 1 & b & b^2 \\ 1 & c & c^2 \\ \end{vmatrix} \), then the value of \( A \) is:

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\textbf{Tip:} Recognize Vandermonde determinant patterns—they often simplify complex-looking problems instantly.
Updated On: Jan 13, 2026
  • \( (a - b)(b - c)(c - a) \)
  • \( (a - b)(b - c)(a - c) \)
  • \( (a + b)(b + c)(c + a) \)
  • \( (b - a)(c - b)(c - a) \)
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The Correct Option is A

Solution and Explanation

To solve the problem, we must evaluate the determinant of the 3x3 matrix:

\( A = \begin{vmatrix} 1 & a & a^2 \\ 1 & b & b^2 \\ 1 & c & c^2 \end{vmatrix} \)

The determinant of this matrix type is evaluated using the formula:

\( A = 1 \cdot \begin{vmatrix} b & b^2 \\ c & c^2 \end{vmatrix} - a \cdot \begin{vmatrix} 1 & b^2 \\ 1 & c^2 \end{vmatrix} + a^2 \cdot \begin{vmatrix} 1 & b \\ 1 & c \end{vmatrix} \)

Calculate each 2x2 determinant:

\( \begin{vmatrix} b & b^2 \\ c & c^2 \end{vmatrix} = bc^2 - b^2c = c \cdot b(c - b) \)

\( \begin{vmatrix} 1 & b^2 \\ 1 & c^2 \end{vmatrix} = 1\cdot c^2 - 1\cdot b^2 = c^2 - b^2 = (c-b)(c+b) \)

\( \begin{vmatrix} 1 & b \\ 1 & c \end{vmatrix} = 1\cdot c - 1\cdot b = c - b \)

Substitute these back into the equation for \( A \):

\( A = 1 \cdot c \cdot b(c - b) - a \cdot (c-b)(c+b) + a^2 \cdot (c-b) \)

Factor out \((c-b)\) from each term:

\( A = (c-b) \left( bc - ab - a(b+c) + a^2 \right) \)

Simplify the expression within the parentheses:

\( = (c-b) \left( bc - ab - ab - ac + a^2 \right) \)

\( = (c-b) \left( a^2 - a(b + c) + bc \right) \)

The expression can be factored further to yield:

\( A = (a-b)(b-c)(c-a) \)

The final answer is:

\( (a-b)(b-c)(c-a) \)
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