5. \(\frac{m+3}{5m^2n}+\frac{2n^2-3}{10mn^2}\)

Общий знаменатель — \(10m^2n^2\):

\[\frac{m+3}{5m^2n}+\frac{2n^2-3}{10mn^2}=\frac{2n(m+3)+m(2n^2-3)}{10m^2n^2}=\frac{2mn+6n+2mn^2-3m}{10m^2n^2}.\]

Ответ: \(\frac{2mn+6n+2mn^2-3m}{10m^2n^2}\).