120. \(\left(4a-\frac{2a}{a+1}\right):\frac{a+1}{2a^2}\)

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

\(\frac{2a(2a+1)}{a+1}:\frac{a+1}{2a^2}=\frac{2a(2a+1)}{a+1}\cdot\frac{2a^2}{a+1}=\frac{4a^3(2a+1)}{(a+1)^2}\).

Ответ: \(\frac{4a^3(2a+1)}{(a+1)^2}\).