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1. Answer:

   { x ∈ Z | x < -20 }

   Step-by-step explanation:

   Set-builder notation is used in math to describe a set by saying what properties its members have.

   It uses curly brackets called “braces”.

   The first part after the first curly bracket tells you what set of numbers x belongs to.  

   The ∈ symbol means “is an element of”.  

   For example:

   • x ∈ N  means “x is an element of the set of Natural numbers”.
   • x ∈ Z  means “x is an element of the set of Integers”.
   • x ∈ R  means “x is an element of the set of Real numbers”.

   This is followed by “|” or “:” which means “such that”.

   This is then followed by the conditions of x, for example:

   • x < 2  means “x is less than 2”.
   • -1 < x < 1  means “x is greater than -1 and less than 1”.

   Therefore, to write the set of all integers less than -20 in set-builder notation:

   • { x ∈ Z | x < -20 }

   This means:  “The set of all x’s that are a member of the Integers, such that x is less than -20”

   Learn more about set notation here:

   https://brainly.com/question/27913822

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