Expert: Abe Mantell - 7/20/2008

Question
How do you know when to use interval notation for numbers on a number line? And when it is simply just two numbers?

Answer
Hello Courtney,

Interval notation is used to spcecify a range of values, not just 1 or 2
values.

For example:
1. the solution to: 2x+1>9 is x>4, so any x value greater than 4
-- solves the equation.  In interval notation, it would be (4, infinity)
2. 2x+1=9 means x=4...only 1 value, not a range of values.

See?

TTYL, Abe