That is saying (-1) is a lowe bound of the function.
It is something but it does not necesseraly say there is no bigger lower bound (inf).
I need to prove that -1 is the biggest lower bound, and there is no else
I need to solve that without sequences.. Havent learnt that yet..
Is there another way?
How are we expected to know what you have studied?
Show that if $\displaystyle \varepsilon > 0$ show that $\displaystyle \exists x_{\varepsilon}$ such that $\displaystyle -1<f\left(x_{\varepsilon}\right)<-1+{\varepsilon}$.