See the documentation for the Limit symbol for more info.
i. Limit[(t^3 + 3t^2 - 12t + 4)/(t^3 - 4t), t -> 2]
ii. For a one-sided limit, is the Direction option.
Limit[(y + 6)/(y^2 - 36), y -> 6, Direction -> -1]
The option value -1 essentially means we treat y as if it's greater than 6, so its value has to decrease in order to approach 6.
