What you are trying to do, I don't know. I will combine them for you.
8)
[tex]\displaystyle \frac{6}{x-1} - \frac{5x}{4} \\ \\ = \frac{4(6)}{4(x-1)} - \frac{5x(x-1)}{4(x-1)} \\ \\
= \frac{24}{4(x-1)} + \frac{-5x(x-1)}{4(x-1)} \\ \\
= \frac{24}{4(x-1)} + \frac{-5x^2+5x}{4(x-1)} \\
= \frac{24 - 5x^2 + 5x}{4(x-1)}[/tex]
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9)
[tex]\displaystyle
\frac{3}{x+7} + \frac{4}{x-8} \\ \\ =
\frac{3(x-8)}{(x+7)(x-8)} + \frac{4(x+7)}{(x+7)(x-8)} \\ \\ =
\frac{3x-24}{(x+7)(x-8)} + \frac{4x+28}{(x+7)(x-8)} \\ \\ =
\frac{3x-24}{(x+7)(x-8)} + \frac{4x+28}{(x+7)(x-8)} \\ \\ =
\frac{7x + 4}{(x+7)(x-8)}[/tex]
