WEBVTT

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Here is the problem: |-3x plus 9| equals 3.

2
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Solve an absolute value equation by splitting it into the cases where the inside is positive or negative.

3
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Write the problem with the absolute value isolated. The absolute value is already alone on one side, so it can be split into cases.

4
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Split into two cases. The inside is either c units above zero or c units below zero.

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Solve the positive case.

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Solve the negative case.

7
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Check each solution in the original equation.

8
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Write the solution set in interval notation.

9
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So the answer is x equals 2 or x equals 4; interval notation: 2, 4.

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An absolute value measures distance from zero, so |u| equals c means u is exactly c units from zero on either side.

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Substituting 2 and 4 gives 3 on the left, matching the right-hand side.