Раскройте скобки: (m-5)(3+m)(m+9)
(m-5)(3+m)(m+9) = (3m+m^2-15-5m)(m+9) = (m^2-2m-15)(m+9) = m^3+9m^2-2m^2-18m-15m-135 = m^3+7m^2-33m-135