25. Intervals b a b a b a b a b a b a b a b a b a b a b a b a Name of Interval Notation Inequality Description Number Line Representation finite, open ( a , b ) a < x < b finite, closed [ a , b ] a x b finite, half-open ( a , b ] [ a , b ) a < x b a x < b infinite, open ( a , ) (- , b ) a < x < - < x < b infinite, closed [ a , ) [- , b ] a x < - < x b