26. \(\left(\frac{a+4}{a-4}-\frac{a-4}{a+4}\right)\cdot\left(\frac14+\frac1a\right)\) при \(a=3,96\)

\[\frac{a+4}{a-4}-\frac{a-4}{a+4}=\frac{16a}{a^2-16},\qquad \frac14+\frac1a=\frac{a+4}{4a}.\]

Тогда:

\[\frac{16a}{a^2-16}\cdot\frac{a+4}{4a}=\frac{4}{a-4}.\]

\[\frac{4}{3.96-4}=\frac{4}{-0.04}=-100.\]

Ответ: −100.