Упростите выражение \(\frac{21m}{25+10m+m^2}\cdot \frac{5+m}{7m^4}\)
\(\frac{3}{m^3(5+m)}\)
\(3m(5+m)\)
\(\frac{147m^9}{(5+m)^3}\)
\(\frac{3m}{15+m^2}\)