Find the Matrix of the Quadratic Form $$6 x _ { 1 } x _ { 2 } - 18 x _ { 1 } x _ { 3 } + 18 x _ { 2 } x _ { 3 }$$

Multiple Choice

Find the matrix of the quadratic form.
- $$6 x _ { 1 } x _ { 2 } - 18 x _ { 1 } x _ { 3 } + 18 x _ { 2 } x _ { 3 }$$

A)
$\left[ \begin{array} { r r r } 0 & 6 & - 18 \\ 6 & 0 & 18 \\ - 18 & 18 & 0 \end{array} \right]$

B)
$\left[\begin{array}{rrr}3 & 0 & 0 \\0 & -9 & 0 \\0 & 0 & 9\end{array}\right]$

C)
$\left[\begin{array}{rrr}0 & 3 & -9 \\3 & 0 & 9 \\-9 & 9 & 0\end{array}\right]$

D)
$$\left[ \begin{array} { r r r } 1 & 3 & - 9 \\3 & 1 & 9 \\- 9 & 9 & 1\end{array} \right]$$