6) a·b-(a+1)(b-1) =ab-ab+a-b+1=a-b+1
334577·446788-334578·446787=334577-446788+1= -112210
7) ab-(a-1)(b+1)=ab-ab-a+b+1=-a+b+1
4593745·9851482-4593746·9851483= -4593745+9851482+1=5257738
8) ab-(a+1)(b-1)=a-b+1
226157·579121-226158·579120=226157-579121+1= -352963
9) ab-(a-1)(b+1)= -a+b+1
346521*600254-346520*600255= -34521+600254+1=565734
10) ab-(a-1)(b-1)=ab-ab+a+b-1=a+b-1
123447*50802-123446*50801=123447+50802-1=174248
11) ab-(a-1)(b+1)= -a+b+1
504030*304050-504029*304051= -504030+304050+1= -199979
12) ab-(a+1)(b-1)=a-b+1
504030*304050-504031*304049=504030-304050+1=199981