Answer Key Objects
The answer key objects (for example, 3.2; (6.45, 6.75]) specify the correct answer for the question.
The Number Line mode uses an intuitive syntax to distinguish between objects on the number line. Note that punctuation endpoints refers to the parentheses and bracket graphing symbols.
To Do This: 
Use This Notation: 
Example 
Notes 

Single closed circle 
Expressed as an evaluated number. 
3.2 

Single open circle 
Expressed as an evaluated number wrapped in parentheses. 
(1.4) 

Punctuation endpoints for intervals 
Expressed as evaluated numbers with the punctuation mark at the appropriate position. 
[1.3, 2.4) 
Intervals are expressed per usual mathematical notation (i.e., the lower and upper bounds are separated by a comma). 
Multiple objects and intervals 
Separated by semicolons. 
3.2; (6.45, 6.75] 

Specify infinity and infinity as left and right endpoints of intervals, respectively. 
(infinity, 3] (5, infinity] 

Specify the answer key as no solution 
no solution 

Specify the answer key as the entire real number line 
(infinity, infinity) 
 Two answer key objects must not be placed so that they are less than 1/4 of the distance between two consecutive tickmarks.
 If an answer key object is overlapping a tickmark but the answer is not actually on the tickmark, your tickmark spacing is too small. Decrease the range attribute to a smaller range.
Below are examples of malformed answer keys and the corrected version.
Malformed Example 
Why? 
Corrected Example 

(3,5];[4,6) 
The intervals overlap. 
(3,6) or (3,4;4,5;5,6) 
3;[2,4] 
3 is in the interval [2,4]. 
[2,4] or [2,3;3,4] 
Syntax examples
Since all values must be evaluated to work, no values should include expressions involving operators that are not evaluated. You must use the <eqn> tag to evaluate expressions. The following examples show the proper syntax for the answer field for both single objects and intervals. In the examples, n is an evaluated number.
Type 
Syntax 
Description 

Single point 
n 
Closed point at x = n 
Single point 
(n) 
Open point at x = n 
Interval 
n0, n1 
Interval between two closed points 
Interval 
(n0), (n1) 
Interval between two open points 
Interval 
n0, n1) 
Interval between a closed point at x = n0 and a right parenthesis at x = n1 
Interval 
(n0, n1 
Interval between a left parenthesis at x = n0 and a closed point at x = n1 
Interval 
[n0, n1] 
Interval between a left bracket at x = n0 and a right bracket at x = n1 
Interval 
(infinity, n 
Interval between the left infinity arrow and a closed point at x = n 
Interval 
n, infinity) 
Interval between a closed point and the right infinity arrow 
Interval 
(infinity, infinity) 
Entire real line 