Find the limit. lim 1/x^2-4

a)x->2^+

b)x->2^-

c)x->-2^+

d)x->-2^-

I'm completely lost. I don't understand how some answers are infinity and the others are negative infinity.

1 answer

well since the fraction approaches 1/0, clearly it will approach either +∞ or -∞

So, just check the denominator to see whether it is positive or negative.

a) x->2+ means x > 2. So, x^2 > 4 and the limit is +∞

similarly for the others.