SAT 代数与高等数学练习题

Advanced Math / Absolute Value Equations

Absolute value as distance and solution counts

Absolute value can model distance on a number line. This viewpoint makes solution counts and tolerance statements easier to interpret.

Least you need to know

  • Distance is always nonnegative.
  • A positive distance from a point gives two locations.
  • A distance of zero gives one location.

Key notation

  • |x-a| — The distance between $x$ and $a$

Worked example

The statement 'x is within 3 units of 10' is $|x-10|\le 3$.

Common mistakes

  • Distance from $a$ is written $|x-a|$, not $|x+a|$.
  • Within means at most, not at least.

How to recognize it

  • The wording includes distance, within, tolerance, or number of solutions.

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