Express the matrix $B=\left[\begin{array}{rrr}2 & -2 & -4 \\ -1 & 3 & 4 \\ 1 & -2 & -3\end{array}\right]$ as the sum of a symmetric and a skew symmetric matrix.

Any square matrix $B$ can be expressed as the sum of a symmetric matrix $P$ and a skew-symmetric matrix $Q$,where $P = \frac{1}{2}(B + B')$ and $Q = \frac{1}{2}(B - B')$.
Given $B = \left[\begin{array}{rrr}2 & -2 & -4 \\ -1 & 3 & 4 \\ 1 & -2 & -3\end{array}\right]$,its transpose is $B' = \left[\begin{array}{rrr}2 & -1 & 1 \\ -2 & 3 & -2 \\ -4 & 4 & -3\end{array}\right]$.
Calculating $P = \frac{1}{2}(B + B') = \frac{1}{2} \left( \left[\begin{array}{rrr}2 & -2 & -4 \\ -1 & 3 & 4 \\ 1 & -2 & -3\end{array}\right] + \left[\begin{array}{rrr}2 & -1 & 1 \\ -2 & 3 & -2 \\ -4 & 4 & -3\end{array}\right] \right) = \frac{1}{2} \left[\begin{array}{rrr}4 & -3 & -3 \\ -3 & 6 & 2 \\ -3 & 2 & -6\end{array}\right] = \left[\begin{array}{rrr}2 & -\frac{3}{2} & -\frac{3}{2} \\ -\frac{3}{2} & 3 & 1 \\ -\frac{3}{2} & 1 & -3\end{array}\right]$.
Since $P' = P$,$P$ is a symmetric matrix.
Calculating $Q = \frac{1}{2}(B - B') = \frac{1}{2} \left( \left[\begin{array}{rrr}2 & -2 & -4 \\ -1 & 3 & 4 \\ 1 & -2 & -3\end{array}\right] - \left[\begin{array}{rrr}2 & -1 & 1 \\ -2 & 3 & -2 \\ -4 & 4 & -3\end{array}\right] \right) = \frac{1}{2} \left[\begin{array}{rrr}0 & -1 & -5 \\ 1 & 0 & 6 \\ 5 & -6 & 0\end{array}\right] = \left[\begin{array}{rrr}0 & -\frac{1}{2} & -\frac{5}{2} \\ \frac{1}{2} & 0 & 3 \\ \frac{5}{2} & -3 & 0\end{array}\right]$.
Since $Q' = -Q$,$Q$ is a skew-symmetric matrix.
Thus,$B = P + Q = \left[\begin{array}{rrr}2 & -\frac{3}{2} & -\frac{3}{2} \\ -\frac{3}{2} & 3 & 1 \\ -\frac{3}{2} & 1 & -3\end{array}\right] + \left[\begin{array}{rrr}0 & -\frac{1}{2} & -\frac{5}{2} \\ \frac{1}{2} & 0 & 3 \\ \frac{5}{2} & -3 & 0\end{array}\right]$.