Absolute value and distance intervals
Absolute value measures distance from zero on the real line.
Key knowledge
For real x, |x| equals x when x≥0 and −x when x<0. The distance from x to a is |x−a|. Thus a distance less than r from a is the open interval from a−r to a+r.
Values and equations
|x| = x if x≥0, −x if x<0; |x−a|<r ⇔ a−r<x<a+r
- x, a
- Real point and interval center
- r
- Positive radius in the same coordinate units
Conditions and scope
- Use real numbers and r>0.
- A distance is nonnegative; |x|=r alone does not select the sign of x.
Real line only. Order-preserving/reversing real operations; no unqualified division by unknown-sign expressions.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Checked the stated absolute value and distance intervals and restrictions against the listed primary sections; exact inspected boundaries are in the author receipt.
2026-10-10 · Independent Physics and Measurement reference editor (AI editorial bounded review). Independent AI editorial review of this entry's statements, equations, applicability conditions and source coverage. Source checks apply to these claims within their stated limits.
Entry details
Permanent link to this entry ↗- Record identity
- foundation-math-absolute-value
- Revision
- foundations-refresh.1
- Structured reference record
- Foundational reference additions