[tex]a)R(x) = \frac{ {x}^{2} - 2x - 15 }{ {x}^{2} - 10x + 25} [/tex]
[tex]R(x) = \frac{ {x}^{2} - 5x + 3x - 15}{ {x}^{2} - 5x - 5x + 25} [/tex]
[tex]R(x) = \frac{x(x - 5) + 3(x - 5)}{x(x - 5) - 5(x - 5)} [/tex]
[tex]R(x) = \frac{(x - 5)(x + 3)}{(x - 5)(x - 5)} [/tex]
[tex]R(x) = \frac{x + 3}{x - 5} [/tex]
[tex]b)R( - 1) = \frac{ - 1 + 3}{ - 1 - 5} = \frac{2}{ - 6} = - \frac{2}{6} = - \frac{1}{3} [/tex]
