Solución
f
′
(
x
)
=
−
x
2
−
18
x
+
64
(
x
2
−
7
x
+
1
)
2
f'\left( x \right) = {{ - {x^2} - 18x + 64} \over {{{\left( {{x^2} - 7x + 1} \right)}^2}}}
f
′
(
x
)
=
(
x
2
−
7
x
+
1
)
2
−
x
2
−
18
x
+
64