# Math Help - the formal definition of limit

1. ## the formal definition of limit

Let
f :Â® Â be given by f ( x) = x2 - 4 . Then lim

x
®-3

( x^2 - 4) = 5.
any help will be appraciated,thanks.

2. Originally Posted by koko2009
Let

f :Â® Â be given by f ( x) = x2 - 4 . Then lim

x
®-3
( x^2 - 4) = 5.
any help will be appraciated,thanks.
$\left|x^2-4-5\right|=\left|x-3\right|\left|x+3\right|$. Now if we only consider a neighborhood of radius $1$ (i.e. $0<|x+3|<1$ then we can say that $|x-3| for some $c$ (find it). Do you get the idea?