(1990)^2 - 1996 = (1990)^2 - 1990 - 6 = (1990 - 3).(1990 + 2) = (1987).(1992)
(1990)^2 + 3980 - 3 = (1990)^2 +2.1990 + 1 - 4 = (1990 +1)^2 - 2^2 = (1991 -2)(1991 + 2) = (1993).(1989)
Assim concluimos que o valor da expressao será igual a 1991