Question 154639
Divide:
{{{(x-8)/(x+5)}}}by{{{(x-9)/(x+4)}}} Invert the second fraction and multiply.
{{{((x-8)/(x+5))*((x+4)/(x-9))}}} 
If you substitute any of the values, -5, 9, or, in the given expression, -4, you will end up with a fraction whose denominator is zero.
This means that you will be dividing by zero and, as you know, division by zero is undefined and thus not allowed.