Express the matrix `A=[{:(-1,5,1),(2,3,4),(7,0,9):}]` as the sum of a symmetric and a skew-symmetric matrix.

Explanation

To express the matrix \( A = \begin{pmatrix} -1 & 5 & 1 \\ 2 & 3 & 4 \\ 7 & 0 & 9 \end{pmatrix} \) as the sum of a symmetric and a skew-symmetric matrix, we can use the following formulas:

1. The symmetric part \( P \) of the matrix \( A \) is given by:
\[ P = \frac{1}{2}(A + A^T) \]

2. The skew-symmetric part \( Q \) of the matrix \( A \) is given by:
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