(a)^2 * (b)^2 = (a * b)^2
Wir lassen also erstmal die Quadrate weg
(1 + a) * (a - 1 + 1/(a + 1))
= a - 1 + 1/(a + 1) + a^2 - a + a/(a + 1)
= - 1 + 1/(a + 1) + a^2 + a/(a + 1)
= - (a + 1)/(a + 1) + 1/(a + 1) + a^2 + a/(a + 1)
= a^2
Das kann men jetzt leicht quadrieren
(a^2)^2 = a^4