Question

Write the interval notation corresponding to the set notation

{x | x < –7}.

Answer 1

Since
[-5,8) is the same as {x|-5=<x<8}
we have
{x|x<-7}
in interval notation
[-infinity, -7)

Answer 2

Thank you, but why is it
(-infinity -7)?

is it translated to
negative infinity - 7?

Answer 3

You are right in actual practice, it is normal to exclude infinity or negative infinity. In my books, -infinity is a short form for negative infinity.

So the correct answer would be:
<b>(negative infinity, -7)</b>

Answer 4

Write the interval notation corresponding to the set notation {x | - 5 < x  4}.