Why is the boundary line dashed for ?
Conditions
- The inequality is strict (>).
- The boundary line is .
Reasoning, step by step
- Identify the inequality .
- Replace the inequality with equality to find the boundary line .
- Observe that the inequality is strict, meaning x cannot equal 3.
- Draw the boundary line as dashed to indicate that points on the line are not included in the solution set.
Example
The narrator says, "Now x being greater than three but not equal to it, instead of drawing a solid line, we're gonna draw a dashed line."
Common misconceptions
- Thinking that the boundary line is part of the solution set.
- Confusing strict inequalities with non-strict inequalities.
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Related questions
For an x-inequality, shade to the right if x is greater than the boundary value ( or ), and shade to the left if x is less than the boundary value ( or ).
Conditions: The inequality restricts x.; The boundary is a vertical line .
To graph , first draw a horizontal boundary line at . Make the line solid because the inequality includes equality.
Conditions: The inequality restricts only one variable (y).; The inequality is non-strict (≤).
An inequality produces a vertical boundary when it restricts only the x-coordinate (e.g., ). It produces a horizontal boundary when it restricts only the y-coordinate (e.g., ).
Conditions: The inequality is in an xy-coordinate system.; The boundary is determined by replacing the inequality with equality.
The boundary line is solid because the inequality includes equality. Since x can be less than or equal to -2, the points on the line are part of the solution set.
Conditions: The inequality is non-strict (≤).; The boundary line is .
The region above is shaded because the inequality requires the y-coordinate to be greater than -4. On a standard coordinate plane, larger y-values are located above the horizontal line .
Conditions: The inequality restricts y.; The boundary is a horizontal line .
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