• ∣a∣=−(a),a<0;∣a∣=a,a>0|a|=-(a), a<0; |a|=a, a>0∣a∣=−(a),a<0;∣a∣=a,a>0
  • Do example 1 p33
  • If ∣x∣<a|x|<a∣x∣<a, then −a<x<a-a<x<a−a<x<aand if ∣x∣≥a|x|\geq a∣x∣≥a, then a≥x≥−aa\geq x \geq -aa≥x≥−a
  • Do exampleDistance between two valuesThe distance between two values is equal to the absolute value of their difference: ∣xa−xb∣|x_a-x_b|∣xa−xb∣