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