Limit and infinity

limit x mendekati 8

Just got this 'story' from twitland

After explaining concept of limit and give example as shown above, the teacher try to test students see if they understood. And the following is the student's answer


hmmm... something wrong?

Off course! First of all, in the example above, its's not clear if x approach 8 from right or left? Approaching 8 from right will give positive infinity but approaching from the left will produce minus infinity!