120. (\(4a - \frac{2a}{a + 1}\)) \cdot \(\frac{a + 1}{2a^2}\).

120. Упростим выражение:

\((4a - \frac{2a}{a + 1}\)) \cdot \(\frac{a + 1}{2a^2}\) = \((\frac{4a(a + 1) - 2a}{a + 1}\)) \cdot \(\frac{a + 1}{2a^2}\) = \((\frac{4a^2 + 4a - 2a}{a + 1}\)) \cdot \(\frac{a + 1}{2a^2}\) = \((\frac{4a^2 + 2a}{a + 1}\)) \cdot \(\frac{a + 1}{2a^2}\) = \(\frac{2a(2a + 1)}{a + 1}\) \cdot \(\frac{a + 1}{2a^2}\) = \(\frac{2a(2a + 1)(a + 1)}{(a + 1)2a^2}\) = \(\frac{2a + 1}{a}\)

Ответ: \(\frac{2a + 1}{a}\)