Determinar A B, A B e A – B quando:
a) A = {x  R / 0 < x < 3} e B = {x  R / 1 < x < 5}
b) A = {x  R / -4 < x  1} e B = {x  R / 2  x  3}
c) A = {x  R / -2  x < 2} e B = {x  R / x  0