Graphing an absolute value inequality involves finding all the numbers that satisfy the inequality and representing them on a number line. The result will either be a segment between two points or two rays extending in opposite directions from two points.
Here's a step-by-step approach:
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Isolate the Absolute Value: If necessary, rewrite the inequality so the absolute value expression is alone on one side. For example, if you have
|x + 2| - 3 < 5
, first add 3 to both sides to get|x + 2| < 8
. -
Create Two Inequalities: An absolute value inequality like
|x| < a
(where 'a' is a positive number) is equivalent to-a < x < a
. Similarly,|x| > a
is equivalent tox < -a
orx > a
. Apply this principle to your specific inequality.-
For
|x + 2| < 8
: This becomes-8 < x + 2 < 8
. -
For
|x - 1| > 3
: This becomesx - 1 < -3
orx - 1 > 3
.
-
-
Solve Each Inequality: Solve each of the inequalities you created in the previous step.
-
For
-8 < x + 2 < 8
: Subtract 2 from all parts:-10 < x < 6
. -
For
x - 1 < -3
orx - 1 > 3
: Add 1 to both sides of each inequality:x < -2
orx > 4
.
-
-
Graph the Solution Set:
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Number Line: Draw a number line.
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Endpoints: Locate the endpoint(s) of your solution(s) on the number line.
-
-10 < x < 6
: Place open circles at -10 and 6. Open circles indicate that the endpoints are not included in the solution (because the inequalities are strict: < or >). -
x < -2
orx > 4
: Place open circles at -2 and 4.
-
-
Shading: Shade the region(s) of the number line that represent the solutions.
-
-10 < x < 6
: Shade the region between -10 and 6. This segment represents all numbers greater than -10 and less than 6. -
x < -2
orx > 4
: Shade the region to the left of -2 and the region to the right of 4. These rays represent all numbers less than -2 or greater than 4.
-
-
Closed Circles: If the original inequality had a "less than or equal to" (≤) or "greater than or equal to" (≥) sign, use closed circles (or brackets) at the endpoints to indicate that those values are included in the solution.
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Example Summary Table:
Inequality | Equivalent Inequality(ies) | Solution | Graph on Number Line |
---|---|---|---|
|x| < 3 |
-3 < x < 3 |
-3 < x < 3 |
(---o========o---) where 'o' represents an open circle at -3 and 3, and '========' represents the shaded region between them. |
|x| ≤ 3 |
-3 ≤ x ≤ 3 |
-3 ≤ x ≤ 3 |
(---[========]---) where '[' and ']' represent closed brackets at -3 and 3, and '========' represents the shaded region between them. |
|x| > 3 |
x < -3 or x > 3 |
x < -3 or x > 3 |
(====o-------o====) where 'o' represents an open circle at -3 and 3, and '====' represents the shaded regions to the left of -3 and to the right of 3. |
|x| ≥ 3 |
x ≤ -3 or x ≥ 3 |
x ≤ -3 or x ≥ 3 |
(====[-------]====) where '[' and ']' represent closed brackets at -3 and 3, and '====' represents the shaded regions to the left of -3 and to the right of 3. |
|x + 1| < 2 |
-2 < x + 1 < 2 |
-3 < x < 1 |
(---o========o---) where 'o' represents an open circle at -3 and 1, and '========' represents the shaded region between them. |
|x - 2| > 1 |
x - 2 < -1 or x - 2 > 1 |
x < 1 or x > 3 |
(====o-------o====) where 'o' represents an open circle at 1 and 3, and '====' represents the shaded regions to the left of 1 and to the right of 3. |
In conclusion, graphing an absolute value inequality involves isolating the absolute value, creating two related inequalities, solving those inequalities, and then representing the solution set as a segment or two rays on a number line, taking care to use open or closed circles/brackets based on the inequality symbols.