Упростите выражение 21-5m/m2-9 - m/m2-9 : m/m+3 - m-3/m+3

1) m/[ (m-3) (m+3) ]:m / (m+3) = m/[ (m-3) (m+3) ] * (m+3) / m=1 / (m-3)

2) (21-5m) / [ (m-3) (m+3) ]-1 / (m-3) - (m-3) / (m+3) =

= (21-2m-m-3-m²+6m-9) / (m²-9) = (9-m²) / (m²-9) = - 1