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2.7 Linear Inequalities and Absolute Value Inequalities

Interval notation, the sign-flip rule when multiplying by a negative, compound inequalities, and splitting an absolute value inequality into two cases.

Algebra and Trigonometry 2e, 2.7 Linear Inequalities and Absolute Value Inequalities

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86 exercises

Using Interval Notation to Express All Real Numbers Greater Than or Equal to a

Use interval notation to indicate all real numbers greater than or equal to −2. −2.

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2.7 Exercise 2

Use interval notation to indicate all real numbers between and including −3 −3 and 5. 5.

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Using Interval Notation to Express All Real Numbers Less Than or Equal to a or Greater Than or Equal to b

Write the interval expressing all real numbers less than or equal to −1 −1 or greater than or equal to 1. 1.

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2.7 Exercise 4

Express all real numbers less than −2 −2 or greater than or equal to 3 in interval notation.

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Demonstrating the Addition Property

Illustrate the addition property for inequalities by solving each of the following:

  1. ⓐ x−15<4 x - 15 < 4
  2. ⓑ 6≥x−1 6 \geq x - 1
  3. ⓒ x+7>9 x + 7 > 9
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2.7 Exercise 6

Solve: 3x−2<1. 3 x −2 < 1.

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Demonstrating the Multiplication Property

Illustrate the multiplication property for inequalities by solving each of the following:

  1. ⓐ 3x<6 3 x < 6
  2. ⓑ −2x−1≥5 −2 x - 1 \geq 5
  3. ⓒ 5−x>10 5 - x > 10
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2.7 Exercise 8

Solve: 4x+7≥2x−3. 4 x + 7 \geq 2 x - 3.

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Solving an Inequality Algebraically

Solve the inequality: 13−7x≥10x−4. 13 - 7 x \geq 10 x - 4.

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2.7 Exercise 10

Solve the inequality and write the answer using interval notation: −x+4< 1 2 x+1. - x + 4 < \frac{1}{2} x + 1.

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Solving an Inequality with Fractions

Solve the following inequality and write the answer in interval notation: − 3 4 x≥− 5 8 + 2 3 x. - \frac{3}{4} x \geq - \frac{5}{8} + \frac{2}{3} x .

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2.7 Exercise 12

Solve the inequality and write the answer in interval notation: − 5 6 x≤ 3 4 + 8 3 x. - \frac{5}{6} x \leq \frac{3}{4} + \frac{8}{3} x .

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Solving a Compound Inequality

Solve the compound inequality: 3≤2x+2<6. 3 \leq 2 x + 2 < 6.

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2.7 Exercise 14

Solve the compound inequality: 4<2x−8≤10. 4 < 2 x - 8 \leq 10.

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2.7 Exercise 16

Solve the compound inequality: 3y<4−5y<5+3y. 3 y < 4 - 5 y < 5 + 3 y .

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2.7 Exercise 18

Describe all x-values within a distance of 3 from the number 2.

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Solving an Absolute Value Inequality

Solve | x−1 |≤3 \left|x - 1\right| \leq 3 .

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2.7 Exercise 22

When solving an inequality, explain what happened from Step 1 to Step 2:

Step 1 −2x>6 Step 2 x<−3 \begin{matrix}\text{Step 1} & - 2 x > 6 \\ \text{Step 2} & x < - 3\end{matrix}

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2.7 Exercise 24

When writing our solution in interval notation, how do we represent all the real numbers?

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2.7 Exercise 26

Describe how to graph y=| x−3 | y = \left|x - 3\right|

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2.7 Exercise 28

Solve the inequality. Write your final answer in interval notation.

3x+2≥7x−1 3 x + 2 \geq 7 x - 1

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2.7 Exercise 30

Solve the inequality. Write your final answer in interval notation.

4(x+3)≥2x−1 4 \left(x + 3\right) \geq 2 x - 1

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2.7 Exercise 32

Solve the inequality. Write your final answer in interval notation.

−5(x−1)+3>3x−4−4x −5 \left(x - 1\right) + 3 > 3 x - 4 - 4 x

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2.7 Exercise 34

Solve the inequality. Write your final answer in interval notation.

x+3 8 − x+5 5 ≥ 3 10 \frac{x + 3}{8} - \frac{x + 5}{5} \geq \frac{3}{10}

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2.7 Exercise 36

Solve the inequality involving absolute value. Write your final answer in interval notation.

| x+9 |≥−6 \left|x + 9\right| \geq −6

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2.7 Exercise 38

Solve the inequality involving absolute value. Write your final answer in interval notation.

|3x−1|>11 \left|3 x - 1\right| > 11

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2.7 Exercise 40

Solve the inequality involving absolute value. Write your final answer in interval notation.

| x−2 |+4≥10 \left|x - 2\right| + 4 \geq 10

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2.7 Exercise 42

Solve the inequality involving absolute value. Write your final answer in interval notation.

|x−7|<−4 \left|x - 7\right| < −4

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2.7 Exercise 44

Solve the inequality involving absolute value. Write your final answer in interval notation.

| x−3 4 |<2 \left|\frac{x - 3}{4}\right| < 2

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2.7 Exercise 46

Describe all the x-values within or including a distance of the given values.

Distance of 3 units from the number 9

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2.7 Exercise 48

Describe all the x-values within or including a distance of the given values.

Distance of 11 units from the number 1

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2.7 Exercise 50

Solve the compound inequality. Express your answer using inequality signs, and then write your answer using interval notation.

3x+1>2x−5>x−7 3 x + 1 > 2 x - 5 > x - 7

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2.7 Exercise 52

Solve the compound inequality. Express your answer using inequality signs, and then write your answer using interval notation.

2x−5<−11or 5x+1≥6 2 x - 5 < −11 \text{or } 5 x + 1 \geq 6

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2.7 Exercise 64

Write the set in interval notation.

{ x| −1<x<3 } \left\{\right. x \left|\right. −1 < x < 3 \left.\right\}

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2.7 Exercise 66

Write the set in interval notation.

{ x| x<4 } \left\{\right. x \left|\right. x < 4 \left.\right\}

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2.7 Exercise 68

Write the interval in set-builder notation.

( −∞,6 ) \left(- \infty , 6\right)

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2.7 Exercise 70

Write the interval in set-builder notation.

[−3,5) \left[−3 , 5\right)

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2.7 Exercise 80

Solve | 3x+1 |=| 2x+3 | \left|3 x + 1\right| = \left|2 x + 3\right|

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2.7 Exercise 82

x−5 x+7 ≤0, \frac{x - 5}{x + 7} \leq 0 , x≠−7 x \neq −7

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2.7 Exercise 84

In chemistry the volume for a certain gas is given by V=20T, V = 20 T , where V is measured in cc and T is temperature in ºC. If the temperature varies between 80ºC and 120ºC, find the set of volume values.

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2.7 Exercise 86

Find the x-intercept and the y-intercept without graphing.

4x−3y=12 4 x - 3 y = 12

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2.7 Exercise 88

Solve for y in terms of x, putting the equation in slope–intercept form.

5x=3y−12 5 x = 3 y - 12

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2.7 Exercise 90

Find the distance between the two points.

( −2,5 )( 4,−1 ) \left(−2 , 5\right) \left(4 , −1\right)

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2.7 Exercise 92

Find the distance between the two points.

Find the distance between the two points (−71,432) \left(−71,432\right) and (511,218) (\text{511},\text{218}) using your calculator, and round your answer to the nearest thousandth.

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2.7 Exercise 94

Find the coordinates of the midpoint of the line segment that joins the two given points.

( −13,5 )\left(−13 , 5\right) and ( 17,18 ) \left(17 , 18\right)

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2.7 Exercise 98

Solve for x. x .

3(x+2)−10=x+4 3 \left(x + 2\right) - 10 = x + 4

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2.7 Exercise 100

Solve for x. x .

12−5(x+1)=2x−5 12 - 5 \left(x + 1\right) = 2 x - 5

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2.7 Exercise 102

Solve for x. x . State all x-values that are excluded from the solution set.

x x 2 −9 + 4 x+3 = 3 x 2 −9 \frac{x}{x^{2} - 9} + \frac{4}{x + 3} = \frac{3}{x^{2} - 9} x≠3,−3 x \neq 3 , −3

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2.7 Exercise 104

Find the equation of the line using the point-slope formula.

Passes through these two points: ( −2,1 ),( 4,2 ). \left(−2 , 1\right) , \left(4 , 2\right) .

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2.7 Exercise 106

Find the equation of the line using the point-slope formula.

Passes through the point ( −3,4 ) \left(- 3 , 4\right) and is parallel to the graph y= 2 3 x+5. y = \frac{2}{3} x + 5.

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2.7 Exercise 108

Write and solve an equation to answer each question.

The number of male fish in the tank is five more than three times the number of females. If the total number of fish is 73, how many of each sex are in the tank?

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2.7 Exercise 110

Write and solve an equation to answer each question.

A truck rental is $25 plus $.30/mi. Find out how many miles Ken traveled if his bill was $50.20.

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2.7 Exercise 112

Use the quadratic equation to solve.

2 x 2 +3x+7=0 2 x^{2} + 3 x + 7 = 0

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2.7 Exercise 114

Name the horizontal component and the vertical component.

−2−i −2 - i

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2.7 Exercise 116

Perform the operations indicated.

( 2+3i )−( −5−8i ) \left(2 + 3 i\right) - \left(- 5 - 8 i\right)

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2.7 Exercise 118

Perform the operations indicated.

−16 +4 −9 \sqrt{- 16} + 4 \sqrt{- 9}

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2.7 Exercise 120

Perform the operations indicated.

(3−5i) 2 \left(3 - 5 i\right)^{2}

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2.7 Exercise 122

Perform the operations indicated.

−2 ( −8 − 5 ) \sqrt{- 2} \left(\sqrt{- 8} - \sqrt{5}\right)

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2.7 Exercise 124

Perform the operations indicated.

3+7i i \frac{3 + 7 i}{i}

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2.7 Exercise 126

Solve the quadratic equation by factoring.

3 x 2 +18x+15=0 3 x^{2} + 18 x + 15 = 0

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2.7 Exercise 128

Solve the quadratic equation by factoring.

7 x 2 −9x=0 7 x^{2} - 9 x = 0

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2.7 Exercise 130

Solve the quadratic equation by using the square-root property.

( x−4 ) 2 =36 \left(x - 4\right)^{2} = 36

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2.7 Exercise 132

Solve the quadratic equation by completing the square.

4 x 2 +2x−1=0 4 x^{2} + 2 x - 1 = 0

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2.7 Exercise 134

Solve the quadratic equation by using the quadratic formula. If the solutions are not real, state No real solution.

15 x 2 −x−2=0 15 x^{2} - x - 2 = 0

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2.7 Exercise 136

Solve the quadratic equation by the method of your choice.

x 2 =10x+3 x^{2} = 10 x + 3

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2.7 Exercise 138

Solve the equations.

x 1 2 −4 x 1 4 =0 x^{\frac{1}{2}} - 4 x^{\frac{1}{4}} = 0

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2.7 Exercise 140

Solve the equations.

3 x 5 −6 x 3 =0 3 x^{5} - 6 x^{3} = 0

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2.7 Exercise 142

Solve the equations.

3x+7 + x+2 =1 \sqrt{3 x + 7} + \sqrt{x + 2} = 1

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2.7 Exercise 144

Solve the equations.

| 2x+3 |−5=9 \left|2 x + 3\right| - 5 = 9

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2.7 Exercise 146

Solve the inequality. Write your final answer in interval notation.

−2x+5>x−7 - 2 x + 5 > x - 7

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2.7 Exercise 148

Solve the inequality. Write your final answer in interval notation.

| 3x+2 |+1≤9 \left|3 x + 2\right| + 1 \leq 9

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2.7 Exercise 150

Solve the inequality. Write your final answer in interval notation.

| x−3 |<−4 \left|x - 3\right| < −4

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2.7 Exercise 152

Solve the compound inequality. Write your answer in interval notation.

3y<1−2y<5+y 3 y < 1 - 2 y < 5 + y

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2.7 Exercise 159

Write the interval notation for the set of numbers represented by { x| x≤9 }. \left\{x \left|\right. x \leq 9\right\} .

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2.7 Exercise 161

Solve for xx: 3( 2x−5 )−3( x−7 )=2x−9. 3 \left(2 x - 5\right) - 3 \left(x - 7\right) = 2 x - 9.

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2.7 Exercise 163

Solve for x: 5 x+4 =4+ 3 x−2 . \frac{5}{x + 4} = 4 + \frac{3}{x - 2} .

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2.7 Exercise 165

Solve for x. Write the answer in simplest radical form.

x 2 3 −x=- 1 2 \frac{x^{2}}{3} - x = - \frac{1}{2}

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2.7 Exercise 167

Solve: | 2x+3 |<5. \left|2 x + 3\right| < 5.

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2.7 Exercise 169

Find the equation of the line with the given information.

Passes through the points ( −4,2 ) \left(- 4 , 2\right) and ( 5,−3 ). \left(5 , −3\right) .

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2.7 Exercise 171

Find the equation of the line with the given information.

Passes through the point ( 2,1 ) \left(2 , 1\right) and is perpendicular to y=− 2 5 x+3. y = - \frac{2}{5} x + 3.

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2.7 Exercise 173

Find the equation of the line with the given information.

Simplify: −4 +3 −16 . \sqrt{−4} + 3 \sqrt{−16} .

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2.7 Exercise 175

Find the equation of the line with the given information.

Divide: 4−i 2+3i . \frac{4 - i}{2 + 3 i} .

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2.7 Exercise 177

Find the equation of the line with the given information.

Solve: ( 3x−1 ) 2 −1=24. \left(3 x - 1\right)^{2} - 1 = 24.

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2.7 Exercise 179

Find the equation of the line with the given information.

Solve: 4 x 2 −4x−1=0 4 x^{2} - 4 x - 1 = 0

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2.7 Exercise 181

Find the equation of the line with the given information.

Solve: 2+ 12−2x =x 2 + \sqrt{12 - 2 x} = x

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2.7 Exercise 183

Find the real solutions of each equation by factoring.

2 x 3 − x 2 −8x+4=0 2 x^{3} - x^{2} - 8 x + 4 = 0

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Adapted from College Algebra © 2021 Rice University. Licensed under CC BY 4.0. Sources: College Algebra 2e, Algebra and Trigonometry 2e, Precalculus 2e, College Algebra with Corequisite Support 2e. Imported at revision 4922e46.