1)6/(a-3)-3/(a-1)-(a+1)/(a²-4a+3)=6/(a-3)-3/(a-1)-(a+1)-(a+1)/(a-3)(a-1)=
=(6a-6-3a+9-a-1)/(a-3)(a-1)=(2a+2)/(a-3)(a-1)=2(a+1)/9a-3)(a-1)
a²-4a+3=(a-1)(a-3)
a1+a2=4 U a1*a2=3⇒a1=1 U a2=3
2)[(a+1)/(a-3)]^-1=(a-3)/(a+1)
3)2(a+1)/(a-3)(a-1) *(a-3)/(a+1)=2/(a-1)