- The modulus of x, |x| equals the maximum of x and –x
- For any two real numbers 'a' and 'b',
|a|+|b| ≥ |a+b|
|a|-|b| ≤ |a-b|
|a.b| = |a| |b|
- If |x| ≤ k then the value of x lies between –k and k, or –k ≤ x ≤ k
- If |x| ≥ k then x ≥ k or x ≤ -k
- For any real number 'a', $$a^2$$ = $$|a|^2$$
