\(\frac{x^{2}-5 x+4}{x^{2}-16}= \frac{(x-1)(x-4)}{(x-4)(x+4)}=\frac{x-1}{x+4}\)
\(\frac{x^{2}+2 a x+a^{2}}{x+a}= \frac{(x+a)^2}{x+a}=x+a\)
\( \frac{x^{4}+2 x^{3}-63 x^{2}}{x^{2}-7 x}= \frac{x^2(x^{2}+2 x-63 )}{x(x-7)}= \frac{x(x^{2}+2 x-63 )}{x-7}\)
\(= \frac{x(x+9)(x-7)}{x-7}=x(x+9)\)