ANSWER
[tex]\frac{5 - x}{x + 2}[/tex]
EXPLANATION
We want to simplify the rational expression:
[tex]( \frac{1}{x - 4)} )( \frac{ - {x}^{2} + 9x - 20}{x + 2} )[/tex]
We split the middle term to obtain:
[tex]( \frac{1}{x - 4)} )( \frac{ - {x}^{2} + 5x + 4x- 20}{x + 2} )[/tex]
We now factor to obtain;
[tex]( \frac{1}{x - 4)} )( \frac{-x(x - 5) + 4(x - 5)}{x + 2} )[/tex]
[tex]( \frac{1}{x - 4)} )( \frac{(x - 5)(4 - x)}{x + 2} )[/tex]
Or
[tex]( \frac{1}{x - 4)} ) ( \frac{ - (x - 5)(x - 4)}{x + 2} )[/tex]
We cancel the common factors to get;
[tex]\frac{ - (x - 5)}{x + 2}[/tex]
[tex] = \frac{5 - x}{x + 2}[/tex]
