Pre-Algebra Examples

$| 2 x + 7 | > 27$

Step 1

Write $| 2 x + 7 | > 27$ as a piecewise.

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Step 1.1

To find the interval for the first piece, find where the inside of the absolute value is non-negative.

$2 x + 7 \geq 0$

Step 1.2

Solve the inequality.

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Step 1.2.1

Subtract $7$ from both sides of the inequality.

$2 x \geq - 7$

Step 1.2.2

Divide each term in $2 x \geq - 7$ by $2$ and simplify.

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Step 1.2.2.1

Divide each term in $2 x \geq - 7$ by $2$ .

$\frac{2 x}{2} \geq \frac{- 7}{2}$

Step 1.2.2.2

Simplify the left side.

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Step 1.2.2.2.1

Cancel the common factor of $2$ .

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Step 1.2.2.2.1.1

Cancel the common factor.

$\frac{2 x}{2} \geq \frac{- 7}{2}$

Step 1.2.2.2.1.2

Divide $x$ by $1$ .

$x \geq \frac{- 7}{2}$

Step 1.2.2.3

Simplify the right side.

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Step 1.2.2.3.1

Move the negative in front of the fraction.

$x \geq - \frac{7}{2}$

Step 1.3

In the piece where $2 x + 7$ is non-negative, remove the absolute value.

$2 x + 7 > 27$

Step 1.4

To find the interval for the second piece, find where the inside of the absolute value is negative.

$2 x + 7 < 0$

Step 1.5

Solve the inequality.

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Step 1.5.1

Subtract $7$ from both sides of the inequality.

$2 x < - 7$

Step 1.5.2

Divide each term in $2 x < - 7$ by $2$ and simplify.

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Step 1.5.2.1

Divide each term in $2 x < - 7$ by $2$ .

$\frac{2 x}{2} < \frac{- 7}{2}$

Step 1.5.2.2

Simplify the left side.

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Step 1.5.2.2.1

Cancel the common factor of $2$ .

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Step 1.5.2.2.1.1

Cancel the common factor.

$\frac{2 x}{2} < \frac{- 7}{2}$

Step 1.5.2.2.1.2

Divide $x$ by $1$ .

$x < \frac{- 7}{2}$

Step 1.5.2.3

Simplify the right side.

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Step 1.5.2.3.1

Move the negative in front of the fraction.

$x < - \frac{7}{2}$

Step 1.6

In the piece where $2 x + 7$ is negative, remove the absolute value and multiply by $- 1$ .

$- (2 x + 7) > 27$

Step 1.7

Write as a piecewise.

${\begin{cases} 2 x + 7 > 27 & x \geq - \frac{7}{2} \\ - (2 x + 7) > 27 & x < - \frac{7}{2} \end{cases}$

Step 1.8

Simplify $- (2 x + 7) > 27$ .

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Step 1.8.1

Apply the distributive property.

${\begin{cases} 2 x + 7 > 27 & x \geq - \frac{7}{2} \\ - (2 x) - 1 \cdot 7 > 27 & x < - \frac{7}{2} \end{cases}$

Step 1.8.2

Multiply $2$ by $- 1$ .

${\begin{cases} 2 x + 7 > 27 & x \geq - \frac{7}{2} \\ - 2 x - 1 \cdot 7 > 27 & x < - \frac{7}{2} \end{cases}$

Step 1.8.3

Multiply $- 1$ by $7$ .

${\begin{cases} 2 x + 7 > 27 & x \geq - \frac{7}{2} \\ - 2 x - 7 > 27 & x < - \frac{7}{2} \end{cases}$

Step 2

Solve $2 x + 7 > 27$ for $x$ .

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Step 2.1

Move all terms not containing $x$ to the right side of the inequality.

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Step 2.1.1

Subtract $7$ from both sides of the inequality.

$2 x > 27 - 7$

Step 2.1.2

Subtract $7$ from $27$ .

$2 x > 20$

Step 2.2

Divide each term in $2 x > 20$ by $2$ and simplify.

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Step 2.2.1

Divide each term in $2 x > 20$ by $2$ .

$\frac{2 x}{2} > \frac{20}{2}$

Step 2.2.2

Simplify the left side.

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Step 2.2.2.1

Cancel the common factor of $2$ .

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Step 2.2.2.1.1

Cancel the common factor.

$\frac{2 x}{2} > \frac{20}{2}$

Step 2.2.2.1.2

Divide $x$ by $1$ .

$x > \frac{20}{2}$

Step 2.2.3

Simplify the right side.

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Step 2.2.3.1

Divide $20$ by $2$ .

$x > 10$

Step 3

Solve $- 2 x - 7 > 27$ for $x$ .

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Step 3.1

Move all terms not containing $x$ to the right side of the inequality.

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Step 3.1.1

Add $7$ to both sides of the inequality.

$- 2 x > 27 + 7$

Step 3.1.2

Add $27$ and $7$ .

$- 2 x > 34$

Step 3.2

Divide each term in $- 2 x > 34$ by $- 2$ and simplify.

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Step 3.2.1

Divide each term in $- 2 x > 34$ by $- 2$ . When multiplying or dividing both sides of an inequality by a negative value, flip the direction of the inequality sign.

$\frac{- 2 x}{- 2} < \frac{34}{- 2}$

Step 3.2.2

Simplify the left side.

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Step 3.2.2.1

Cancel the common factor of $- 2$ .

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Step 3.2.2.1.1

Cancel the common factor.

$\frac{- 2 x}{- 2} < \frac{34}{- 2}$

Step 3.2.2.1.2

Divide $x$ by $1$ .

$x < \frac{34}{- 2}$

Step 3.2.3

Simplify the right side.

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Step 3.2.3.1

Divide $34$ by $- 2$ .

$x < - 17$

Step 4

Find the union of the solutions.

$x < - 17$ or $x > 10$

Step 5

The result can be shown in multiple forms.

Inequality Form:

$x < - 17 or x > 10$

Interval Notation:

$(- \infty, - 17) \cup (10, \infty)$

Step 6