First multiply them together
[tex] \left[\begin{array}{ccc}a-6&2&ab\\2&1&5b\\-3&1+3b&2\end{array}\right] [/tex]
A symmetric matrix is where the transpose is equal to original matrix.
This means row n = column n
Looking at row1 = column1 ----> ab = -3
Looking at row2 =column2 ----> 5b = 1+3b
Solve those 2 equations for a,b
b = 1/2
a = -6
