<aside> ⚡ Strategy used to estimate an expression when you cannot determine the exact value

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• Idea is to make your estimate close to the exact value while ensuring that your estimate falls on a particular side of that value, called the “Safe Side”
• Since your estimate could be above or below the exact value, there are two different versions of the Safe Side Strategy depending on which side is the Safe Side:
  • Overestimating the value
  • Underestimating the value

Upper and Lower Bound Estimation

An upper bound for a function $f(x)$ on an interval $I$ is a number $U$ such that $f(x) ≤ U$ for all $x \in I$

A lower bound for a function $f(x)$ on an interval $I$ is a number $L$ such that $f(x) ≥ L$ for all $x \in I$

Absolute Value

For any number $a$, the absolute value of $a$ is

• Product Rule: $|ab| = |a||b|$
• Triangle Inequality: $|a+b| ≤ |a| + |b|$