Calculus help

Question

Write the set of points from -7 to -1 but excluding -4 and -1 as a union of intervals.

Answer 1

Normally, the set of numbers from -7 to -1 would be written as [-7, -1].  (I am assuming based on context that -7 and -1 would be included before we consider the excluded values.)

 

Excluding the -1 simply changes the interval to [-7, -1).

 

Excluding the -4 changes the interval into two intervals, one on either side of -4.  The union of intervals would be [-7,-4)U(-4,-1)