# Why is this support interval not (-1, 1) of 1-x^2 for x < 1?

https://en.wikipedia.org/wiki/Support_(mathematics)

From the closed support section, we see that between at -1 or 1 $1-x^2$ is 0, yet we say the support is [-1, 1] and not (-1, 1)? I thought a support was the set of the domain which does not map to 0?

Further it talks to the closure of the set ... why is the set closure not also (-1, 1)?

• This question is ff topic for this site. Apr 6 '18 at 23:04