In this lesson, we'll learn how to solve equations that contain absolute value expressions.
For example, let's consider the following equation:
For this equation to be true, either the positive or negative of the expression inside the absolute value must equal the right-hand side. That is,
So, let's solve these two equations:
- First, we solve the equation
- Then, we solve the equation
Therefore, the solutions to our original absolute value equation are and
So, we've seen that the solutions to the equation
are and
We can verify that these solutions are correct by substituting them back into the original equation and checking we get a true statement:
Substituting into our equation, we get Therefore, is indeed a solution to the absolute value equation.
Substituting into our equation, we get Therefore, is indeed a solution to the absolute value equation.
Therefore, and are both solutions to our absolute value equation.
Solve the equation
Either the positive or negative of the expression inside the absolute value must be equal to the right-hand side of the equation.
So, we set up the two corresponding equations and solve them independently:
If we obtain:
If we obtain:
Therefore, the solutions are and We can write this more compactly as
If $|z-2| = 3,$ then $z =$
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a
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$-5$ only |
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b
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$-5$ or $ -1$ |
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c
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$-1$ or $5$ |
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d
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$1$ or $5$ |
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e
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$1$ only |
Written in ascending order, the solutions to $|7z| = 42$ are $z =$
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a
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b
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c
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d
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e
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Written in ascending order, the solutions to $\left|\dfrac t8\right| = 9$ are $t =$
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a
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b
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c
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d
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e
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Solve the equation
Either the positive or negative of the expression inside the absolute value must be equal to the right-hand side of the equation.
So, we set up the two corresponding equations and solve them independently:
If we obtain:
If we obtain:
Therefore, the solutions are and
Written in ascending order, the solutions to $|3z+7| = 5$ are $z =$
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a
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b
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c
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d
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e
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Written in ascending order, the solutions to $|3x-4| = 1$ are $x =$
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a
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b
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c
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d
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e
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Solve the equation
Either the positive or negative of the expression inside the absolute value must be equal to the right-hand side of the equation.
So, we set up the two corresponding equations and solve them independently:
If we obtain:
If we obtain:
Therefore, the solutions are and
Written in ascending order, the solutions to $|2-k| = 9$ are $k =$
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a
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b
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c
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d
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e
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If $|4-3x| = 14,$ then $x=$
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a
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$\pm 6$ |
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b
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$\dfrac{10}3$ only |
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c
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$-6$ only |
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d
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$-6$ or $\dfrac{10}3$ |
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e
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$-\dfrac{10}3$ or $6$ |
Solve the equation
Either the positive or negative of the expression inside the absolute value must be equal to the right-hand side of the equation.
So, we set up the two corresponding equations and solve them independently:
If we obtain: Multiplying both sides of the equation by gives
If we obtain: Multiplying both sides of the equation by gives
Therefore, the solutions are and
Written in ascending order, the solutions to $\left| \dfrac{1}{2}x + 3 \right| = 5$ are $x =$
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a
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b
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c
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d
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e
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If $\left\vert 4-\dfrac32x \right\vert = 2,$ then $x=$
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a
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$\dfrac43$ or $4$ |
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b
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$4$ only |
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c
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$-2$ only |
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d
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$-2$ or $\dfrac43$ |
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e
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$-2$ or $4$ |