2nd October 2019

15

# Is a closed circle a bracket or parenthesis?

Interval notation uses brackets [ ] to show the closed circles; the numbers in the parentheses represent the ends of the shaded area. On the number line, there is a closed circle at a and the number line is shaded to the left.

Similarly, how do you know whether to use an open circle or closed circle when graphing an inequality?

Here are some tips for graphing inequalities on a number line. Use an open circle to show that a value is not a solution for the inequality. You will use open circles to graph inequalities that include the symbols >or <. Use a closed circle to show that a value is a solution for the inequality.

What is the difference between an open dot and a closed dot on a number line?

1) Draw a number line. 2) Put either an open circle or a closed dot above the number given. For ≤ and ≥ , use a closed dot to indicate the number itself is part of the solution. For < and >, use an open circle to indicate the number itself is not part of the solution.

What is the difference between a closed dot and an open dot?

A closed (solid) dot means the endpoint is included in the curve and an open dot means it isn't. It's like the difference between "less than or equal to" and "less than". In the graph you show, both dots are open which means the function doesn't have any value, so isn't defined, at x_0.