(2a+6)/(a2-4a+4)×(a-2)/(a2+3a)-(1/a-2)
=2(a+3)/(a-2)² × (a-2)/[a(a+3)] - 1/(a-2)
=2/[a(a-2)] - 1/(a-2)
=(2-a)/[a(a-2)]
=-1/a
=-1÷(1/3)
=-3