Posted by Jen on .
Please solve for the interval notation corresponding to the set notation
{x  x < –7}

Algebra 
MathMate,
See answer to Rachale's question.
http://www.jiskha.com/display.cgi?id=1243987256 
Algebra 
Jen,
Thank you, but why is it
(infinity 7)?
is it translated to
negative infinity  7? 
Algebra 
MathMate,
> [5,8) is the same as {x5=<x<8}
meaning that the square bracket [ includes the lower limit, while the ] includes the upper limit. The limits are separated by a comma.
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:
(negative infinity, 7) 
Algebra 
Jen,
Thank you for the explanation!