If x, y, z are distinct real numbers and \( \left| \begin{array}{ccc} x & x^2 & 2 + x^3 \\ y & y^2 & 2 + y^3 \\ z & z^2 & 2 + z^3 \end{array} \right| = 0 \) then xyz =
Step-by-step Solution:
We are given the determinant equation:
\[
\left| \begin{array}{ccc}
x & x^2 & 2 + x^3 \\
y & y^2 & 2 + y^3 \\
z & z^2 & 2 + z^3
\end{array} \right| = 0
\]
Step 1: Expand the Determinant
Consider the determinant expansion along the third column:
\[
D = \begin{vmatrix} x & x^2 & 2 + x^3 \\ y & y^2 & 2 + y^3 \\ z & z^2 & 2 + z^3 \end{vmatrix}.
\]
We can rewrite the third column as:
\[
\begin{bmatrix} 2 + x^3 \\ 2 + y^3 \\ 2 + z^3 \end{bmatrix} = \begin{bmatrix} x^3 \\ y^3 \\ z^3 \end{bmatrix} + \begin{bmatrix} 2 \\ 2 \\ 2 \end{bmatrix}.
\]
Thus, we express the determinant as:
\[
D = \begin{vmatrix} x & x^2 & x^3 \\ y & y^2 & y^3 \\ z & z^2 & z^3 \end{vmatrix} + \begin{vmatrix} x & x^2 & 2 \\ y & y^2 & 2 \\ z & z^2 & 2 \end{vmatrix}.
\]
Step 2: Evaluate the Determinants
The first determinant,
\[
\begin{vmatrix} x & x^2 & x^3 \\ y & y^2 & y^3 \\ z & z^2 & z^3 \end{vmatrix}
\]
is a Vandermonde determinant, which evaluates to:
\[
(x - y)(y - z)(z - x) xyz.
\]
The second determinant,
\[
\begin{vmatrix} x & x^2 & 2 \\ y & y^2 & 2 \\ z & z^2 & 2 \end{vmatrix},
\]
has all elements in the last column equal to 2. Factoring out the common term:
\[
2 \begin{vmatrix} x & x^2 & 1 \\ y & y^2 & 1 \\ z & z^2 & 1 \end{vmatrix}.
\]
This is another Vandermonde determinant, evaluated as:
\[
2 (x - y)(y - z)(z - x).
\]
Since the given determinant is 0, we have:
\[
(x - y)(y - z)(z - x) xyz + 2 (x - y)(y - z)(z - x) = 0.
\]
Factoring out \( (x - y)(y - z)(z - x) \), which is nonzero (as \( x, y, z \) are distinct), we get:
\[
xyz + 2 = 0.
\]
Step 3: Solve for \( xyz \)
\[
xyz = -2.
\]
Thus, the required value is:
\(
-2.
\)