a) give an example to show it is possible to have lim(x_sub(n) + y_sub(n)) exist without having lim x_sub(n) or lim y_sub(n) exist
b) give an example to show it is possible to have lim(x_sub(n) * y_sub(n)) exist without having lim x_sub(n) or lim y_sub(n) exist