By <span>(x + 5/x^2 + 9x + 20) you apparently meant the following:
x+5
----------------------
x^2 + 9x + 20
and by
</span><span>(x^2-16/x-4)
x^2-16
you apparently meant ---------------
x - 4
Please use additional parentheses for clarity.
Dividing,
</span> x+5 (x-4)(x+4)
---------------------- * ---------------
x^2 + 9x + 20 x-4
Now, x^2 + 9x + 20 factors into (x+4)(x+5), so what we have now is
(x+5)(x+4)
------------------------- = 1 This is true for all x, so there are no exclusions.
(x+4)(x+5)
Note: The equations written in this questions are not appropriately expressed, however, i will work with hypothetical equations that will enable you to solve any problems of this kind.
Answer:
For the system of equations to be unique, s can take all values except 2 and -2
Step-by-step explanation:

![\left[\begin{array}{ccc}2s&4\\2&s\end{array}\right] \left[\begin{array}{ccc}x_{1} \\x_{2} \end{array}\right] = \left[\begin{array}{ccc}-3 \\6 \end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7D2s%264%5C%5C2%26s%5Cend%7Barray%7D%5Cright%5D%20%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7Dx_%7B1%7D%20%5C%5Cx_%7B2%7D%20%5Cend%7Barray%7D%5Cright%5D%20%3D%20%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7D-3%20%5C%5C6%20%5Cend%7Barray%7D%5Cright%5D)
For the system to have a unique solution, 

Matrix A was expressed in the form of a 2x2
i'm not sure if this helps or not but here you go