Limits to infinity (demonstration)

[Zatticmetal]

Can someone please help me demonstrate:

Lim x → ∞ f(x) = Lim x → -∞ f(-x)

I don't know how to pick delta or epsilon in this cases or how to prove that if we suppose the first tends to "L", the other one does too...

 

[Ishuda]

Can someone please help me demonstrate:

Lim x → ∞ f(x) = Lim x → -∞ f(-x)

I don't know how to pick delta or epsilon in this cases or how to prove that if we suppose the first tends to "L", the other one does too...

What have you done? Please show your work (even if you know it is wrong) so we may help you if you are making a mistake. Also, you should read
http://www.freemathhelp.com/forum/announcement.php?f=27

HINT: Suppose you let t=-x.