Matrix Singularity
1. **State the problem:** We need to find the value of $x$ for which the matrix
$$\begin{pmatrix}8 & x & 0 \\ 4 & 0 & 2 \\ 12 & 6 & 0\end{pmatrix}$$
becomes singular.
2. **Recall the definition:** A matrix is singular if its determinant is zero.
3. **Write the determinant formula for a 3x3 matrix:**
$$\det(A) = a(ei - fh) - b(di - fg) + c(dh - eg)$$
where the matrix is
$$\begin{pmatrix}a & b & c \\ d & e & f \\ g & h & i\end{pmatrix}$$
4. **Identify elements:**
$$a=8, b=x, c=0, d=4, e=0, f=2, g=12, h=6, i=0$$
5. **Calculate the determinant:**
$$\det = 8(0 \cdot 0 - 2 \cdot 6) - x(4 \cdot 0 - 2 \cdot 12) + 0(4 \cdot 6 - 0 \cdot 12)$$
$$= 8(0 - 12) - x(0 - 24) + 0$$
$$= 8(-12) - x(-24)$$
$$= -96 + 24x$$
6. **Set determinant to zero for singularity:**
$$-96 + 24x = 0$$
7. **Solve for $x$:**
$$24x = 96$$
$$x = \frac{96}{24} = 4$$
**Final answer:** The matrix is singular when $x = 4$.