If: $f(x)=|x-3|$ and $g(x)=2$

Solve the inequality $|x-1|<2$

I got a solution of:

$1<x<5,x\in R$

But the solution in the back the book said:

$1<x<5,x\in ^{o}$

Is this a typo or what set is $x\in^{o}$ ?

  • 3
    $\begingroup$ I have never seen that notation before, and my guess is on typo. $\endgroup$
    – Mankind
    Mar 25, 2016 at 1:22
  • $\begingroup$ The solution to $|x-1| < 2$ is $-1 < x < 3$, not $1 < x < 5$. $\endgroup$
    – user169852
    Mar 25, 2016 at 1:39
  • 1
    $\begingroup$ Math fonts can lead to various typesetting issues. This must be one of those. $\endgroup$ Mar 25, 2016 at 1:40

1 Answer 1


This is a typo. It's probably also fine to not say $x \in \mathbb{R}$, since they haven't even specified the domain for $x$ in the problem.


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