Recently I decided to learn calculus on my own and I stumbled across something which I cannot figure why is correct.
Let $f$ be some function for which you know only that if $0<|x-3|<1$, then $|f(x)-5|<0.1$
It is necessary true then that
If $|x-2.5|<0.3$, then $|f(x)-5|<0.1$
I can't for the life of me figure out why that would work.
If $|x-2.5|<0.3$ then $2.2<x<2.8$. Therefore, $2<x<4$, or $|x-3|<1$.