Inequalities with Absolute Values: Solving the problem

Examples with solutions for Inequalities with Absolute Values: Solving the problem

Exercise #1

Given:

∣2x−1∣>−10 \left|2x-1\right|>-10

Which of the following statements is necessarily true?

Video Solution

Step-by-Step Solution

Let's solve the problem:
Step 1: Recognize that the inequality we are dealing with is ∣2x−1∣>−10 \left|2x-1\right| > -10 .
Step 2: Consider the nature of absolute values: for any real xx, ∣2x−1∣\left|2x-1\right| is always non-negative (i.e., ≥0\geq 0).
Step 3: Observe that the right side of the inequality, −10-10, is negative. Therefore, the inequality ∣2x−1∣>−10\left|2x-1\right| > -10 is always true because ∣2x−1∣\left|2x-1\right| as a non-negative quantity will always be greater than any negative number.
Step 4: Since the inequality condition always holds true, this means that the statement is valid for all xx.

Therefore, the correct answer is that the inequality holds for all xx.

The solution to the problem is For all x.

Answer

For all x

Exercise #2

Given:

∣4x+12∣>16 \left|4x+12\right|>16

Which of the following statements is necessarily true?

Video Solution

Step-by-Step Solution

To solve this inequality, we use the principle that if ∣A∣>B |A| > B , then A>B A > B or A<−B A < -B . Here's a detailed step-by-step solution:

  • Set up the two inequalities from the absolute value expression:
    1. 4x+12>16 4x + 12 > 16
    2. 4x+12<−16 4x + 12 < -16
  • For the first inequality, 4x+12>16 4x + 12 > 16 :
    - Subtract 12 from both sides to isolate the term with x x :
    4x>16−12 4x > 16 - 12
    4x>4 4x > 4
    - Divide both sides by 4:
    x>1 x > 1
  • For the second inequality, 4x+12<−16 4x + 12 < -16 :
    - Subtract 12 from both sides:
    4x<−16−12 4x < -16 - 12
    4x<−28 4x < -28
    - Divide both sides by 4:
    x<−7 x < -7
  • The solution is the union of both results:
    x>1 x > 1 or x<−7 x < -7

Therefore, the correct answer among the given choices is x>1 x > 1 or x<−7 x < -7 .

Answer

x>1 x>1 or x<−7 x<-7

Exercise #3

Given:

∣5x−10∣>15 \left|5x-10\right|>15

Which of the following statements is necessarily true?

Video Solution

Step-by-Step Solution

To solve the inequality ∣5x−10∣>15 \left|5x-10\right| > 15 , we rewrite it as two separate inequalities:

  • First inequality: 5x−10>15 5x - 10 > 15
  • Second inequality: 5x−10<−15 5x - 10 < -15

Let's solve each one:

For the first inequality 5x−10>15 5x - 10 > 15 :
Add 10 to both sides: 5x>255x > 25
Divide both sides by 5: x>5x > 5

For the second inequality 5x−10<−15 5x - 10 < -15 :
Add 10 to both sides: 5x<−55x < -5
Divide both sides by 5: x<−1x < -1

Combining these solutions, we have:
x>5x > 5 or x<−1x < -1

Therefore, the correct statement regarding the solution set is: x>5 x > 5 or x<−1 x < -1 .

Answer

x>5 x>5 or x<−1 x<-1

Exercise #4

Given:

∣3x+9∣<18 \left|3x+9\right|<18

Which of the following statements is necessarily true?

Video Solution

Step-by-Step Solution

To solve the inequality ∣3x+9∣<18\left|3x + 9\right| < 18, follow these steps:

  • Step 1: Remove the absolute value by expressing it as a double inequality:
    −18<3x+9<18 -18 < 3x + 9 < 18 .

  • Step 2: Simplify the inequality:
    First, subtract 9 from all parts:
    −18−9<3x+9−9<18−9 -18 - 9 < 3x + 9 - 9 < 18 - 9 ,
    which simplifies to −27<3x<9 -27 < 3x < 9 .

  • Step 3: Solve for xx by dividing the entire inequality by 3:
    −273<3x3<93 -\frac{27}{3} < \frac{3x}{3} < \frac{9}{3} ,
    resulting in −9<x<3 -9 < x < 3 .

Upon solving, we determine that the solution to the inequality is the interval:

−9<x<3 -9 < x < 3 .

Answer

−9<x<3 -9 < x < 3

Exercise #5

Given:

∣2x−4∣<8 \left|2x-4\right|<8

Which of the following statements is necessarily true?

Video Solution

Step-by-Step Solution

To solve the absolute value inequality ∣2x−4∣<8 |2x - 4| < 8 , we begin by removing the absolute value expression. This gives us a compound inequality:

−8<2x−4<8-8 < 2x - 4 < 8.

We will solve this compound inequality by handling each part separately:

  • Start with the left inequality: −8<2x−4-8 < 2x - 4.
    • Add 4 to both sides to isolate the term with x x : −8+4<2x-8 + 4 < 2x.
    • Simplify: −4<2x-4 < 2x.
    • Finally, divide both sides by 2: −2<x-2 < x.
  • Now, solve the right inequality: 2x−4<82x - 4 < 8.
    • Add 4 to both sides to isolate the term with x x : 2x−4+4<8+42x - 4 + 4 < 8 + 4.
    • Simplify: 2x<122x < 12.
    • Finally, divide both sides by 2: x<6x < 6.

Combining the two solutions from the parts, we find:

−2<x<6-2 < x < 6.

The solution indicates that x x must be greater than -2 and less than 6. This form matches answer choice 4. Therefore, the correct solution is:

−2<x<6-2 < x < 6.

Answer

−2<x<6 -2 < x < 6

Exercise #6

Given:

∣x−5∣>−11 \left|x-5\right|>-11

Which of the following statements is necessarily true?

Video Solution

Step-by-Step Solution

The absolute value expression ∣x−5∣>−11 \left| x - 5 \right| > -11 inherently suggests that for any real number x x , the inequality holds.

Since the absolute value of any expression is always non-negative and −11-11 is negative, the condition ∣x−5∣>−11 \left| x - 5 \right| > -11 is always satisfied regardless of the choice of x x .

Thus, there is no specific limitation or exceptional circumstance that confines x x to any particular subset of the real numbers.

This implies that no particular statement about x x being greater, less, or constrained to a specific domain can be justified. Therefore, the notion of any statement being "necessarily true" in the conventional sense of constraining x x does not apply.

The correct answer, therefore, is: all x x .

Answer

all x x

Exercise #7

Given:

∣x−5∣>11 \left|x-5\right|>11

Which of the following statements is necessarily true?

Video Solution

Step-by-Step Solution

To solve the inequality ∣x−5∣>11\left|x-5\right| > 11, we first apply the property of absolute values:

  • If ∣A∣>B\left|A\right| > B, then A>BA > B or A<−BA < -B.

Therefore, for ∣x−5∣>11\left|x-5\right| > 11, we have two cases to consider:

  • Case 1: x−5>11x-5 > 11
  • Case 2: x−5<−11x-5 < -11

Let's solve each case separately:

Case 1: x−5>11x-5 > 11

Add 5 to both sides to isolate xx:
x>11+5x > 11 + 5

This simplifies to:

x>16x > 16

Case 2: x−5<−11x-5 < -11

Add 5 to both sides to isolate xx:
x<−11+5x < -11 + 5

This simplifies to:

x<−6x < -6

Thus, the solution to the inequality is:

x>16x > 16 or x<−6x < -6

Comparing this result with the given answer choices, the correct one is:

x>16 x>16 o x<−6 x<-6

Therefore, the solution to the problem is x>16x > 16 or x<−6x < -6.

Answer

x>16 x>16 or x<−6 x<-6

Exercise #8

Given:

∣x+4∣>13 \left|x+4\right|>13

Which of the following statements is necessarily true?

Video Solution

Step-by-Step Solution

To solve the inequality ∣x+4∣>13 \left|x + 4\right| > 13 , we use the property of absolute values, which says that for ∣a∣>b \left|a\right| > b , it implies a>b a > b or a<−b a < -b .

Applying this to our problem, we have:

  • x+4>13 x + 4 > 13 or x+4<−13 x + 4 < -13 .

Now, let's solve each inequality separately:

First inequality: x+4>13 x + 4 > 13

Subtract 4 from both sides to isolate x x :

x>13−4 x > 13 - 4

x>9 x > 9

Second inequality: x+4<−13 x + 4 < -13

Subtract 4 from both sides to isolate x x :

x<−13−4 x < -13 - 4

x<−17 x < -17

Therefore, the solution to the inequality ∣x+4∣>13 \left|x + 4\right| > 13 is x>9 x > 9 or x<−17 x < -17 .

The correct answer choice is:

  • x>9 x > 9 or x<−17 x < -17 .

Answer

x>9 x>9 or x<−17 x<-17

Exercise #9

Given:

∣x−4∣<8 \left|x-4\right|<8

Which of the following statements is necessarily true?

Video Solution

Step-by-Step Solution

To solve the inequality ∣x−4∣<8 |x - 4| < 8 , we will break it down into two separate inequalities.

  • First, recognize that ∣x−4∣<8 |x - 4| < 8 means the expression x−4 x - 4 can vary between -8 and 8 without violating the inequality constraint.
  • This gives us two inequalities to solve: −8<x−4 -8 < x - 4 and x−4<8 x - 4 < 8 .

Let's solve each inequality:
1. For −8<x−4 -8 < x - 4 :
- Add 4 to both sides to isolate x x :
−8+4<x→−4<x -8 + 4 < x \rightarrow -4 < x 2. For x−4<8 x - 4 < 8 :
- Add 4 to both sides to isolate x x :
x<8+4→x<12 x < 8 + 4 \rightarrow x < 12

By combining these results, we obtain the solution:
−4<x<12 -4 < x < 12

Therefore, the range of x x that satisfies the inequality ∣x−4∣<8 |x - 4| < 8 is −4<x<12 -4 < x < 12 .

Hence, the correct statement from the given choices is −4<x<12\boxed{-4 < x < 12}.

Answer

−4<x<12 -4 < x < 12

Exercise #10

Given:

∣x+2∣<3 \left|x+2\right|<3

Which of the following statements is necessarily true?

Video Solution

Step-by-Step Solution

To solve the inequality ∣x+2∣<3|x + 2| < 3, we will apply the property of absolute values by rewriting it without the absolute value sign as follows:

Step 1: Transform the absolute value inequality
Using the rule ∣A∣<B|A| < B implies −B<A<B-B < A < B, we write

−3<x+2<3-3 < x + 2 < 3.

Step 2: Solve this compound inequality. We do this by isolating xx as follows:

  • Subtract 2 from all parts: −3−2<x+2−2<3−2-3 - 2 < x + 2 - 2 < 3 - 2.
  • This simplifies to: −5<x<1-5 < x < 1.

Thus, the inequality ∣x+2∣<3|x + 2| < 3 is solved as −5<x<1-5 < x < 1.

The correct solution is contained in choice 3: −5<x<1-5 < x < 1.

Answer

−5<x<1 -5 < x < 1

Exercise #11

Given:

∣x−3∣≤5 |x-3| \leq 5

Which of the following statements is necessarily true?

Step-by-Step Solution

To solve the inequality ∣x−3∣≤5 |x-3| \leq 5 , we need to consider the definition of absolute value inequalities. The inequality ∣a∣≤b |a| \leq b translates to −b≤a≤b -b \leq a \leq b .

Applying this to our expression ∣x−3∣≤5 |x-3| \leq 5 , we have:

−5≤x−3≤5 -5 \leq x-3 \leq 5 .

We add 3 to all parts of the inequality to isolate x x :

−5+3≤x−3+3≤5+3 -5 + 3 \leq x - 3 + 3 \leq 5 + 3

This simplifies to −2≤x≤8 -2 \leq x \leq 8 .

Answer

−2≤x≤8 -2 \leq x \leq 8

Exercise #12

Given:

∣2x+1∣>7 |2x + 1| > 7

Which of the following statements is necessarily true?

Step-by-Step Solution

To solve the inequality ∣2x+1∣>7 |2x + 1| > 7 , we split it into two separate inequalities:

2x+1>7 2x + 1 > 7 or 2x+1<−7 2x + 1 < -7 .

For the first inequality 2x+1>7 2x + 1 > 7 , subtract 1 from both sides:

2x>6 2x > 6

Divide by 2:

x>3 x > 3

For the second inequality 2x+1<−7 2x + 1 < -7 , subtract 1 from both sides:

2x<−8 2x < -8

Divide by 2:

x<−4 x < -4

Therefore, the solution is x>3 x > 3 or x<−4 x < -4 .

Answer

x>3 x > 3 or x<−4 x < -4

Exercise #13

Given:

∣x+5∣<2 |x+5| < 2

Which of the following statements is necessarily true?

Step-by-Step Solution

To solve the inequality ∣x+5∣<2 |x+5| < 2 , apply the property of absolute values which states that ∣a∣<b |a| < b translates to −b<a<b -b < a < b .

Therefore, −2<x+5<2 -2 < x+5 < 2 .

Subtract 5 from all parts of the inequality to isolate x x :

−2−5<x+5−5<2−5 -2 - 5 < x+5 - 5 < 2 - 5

This simplifies to −7<x<−3 -7 < x < -3 .

Answer

−7<x<−3 -7 < x < -3

Exercise #14

Given:

∣3x−2∣≥4 |3x - 2| \geq 4

Which of the following statements is necessarily true?

Step-by-Step Solution

To solve the inequality ∣3x−2∣≥4 |3x - 2| \geq 4 , we separate it into:

3x−2≥4 3x - 2 \geq 4 or 3x−2≤−4 3x - 2 \leq -4 .

For 3x−2≥4 3x - 2 \geq 4 , add 2 to both sides:

3x≥6 3x \geq 6

Divide by 3:

x≥2 x \geq 2

For 3x−2≤−4 3x - 2 \leq -4 , add 2 to both sides:

3x≤−2 3x \leq -2

Divide by 3:

x≤−23 x \leq -\frac{2}{3}

Therefore, the solution is x≥2 x \geq 2 or x≤−23 x \leq -\frac{2}{3} .

Answer

x≥2 x \geq 2 or x≤−23 x \leq -\frac{2}{3}

Exercise #15

Find the absolute value inequality representation for:

∣x+3∣≤5 |x + 3| \leq 5

Step-by-Step Solution

To solve the inequality ∣x+3∣≤5 |x + 3| \leq 5 , we first consider the definition of absolute value inequality ∣A∣≤B |A| \leq B , which is equivalent to −B≤A≤B -B \leq A \leq B .

Applying this definition, we have:

−5≤x+3≤5 -5 \leq x + 3 \leq 5

Next, we isolate x by subtracting 3 from all parts of the inequality:

−5−3≤x+3−3≤5−3 -5 - 3 \leq x + 3 - 3 \leq 5 - 3

This simplifies to:

−8≤x≤2 -8 \leq x \leq 2

Answer

−8≤x≤2 -8 \leq x \leq 2

Exercise #16

Solve the inequality:

∣2x−5∣>7 |2x - 5| > 7

Step-by-Step Solution

To solve ∣2x−5∣>7 |2x - 5| > 7 , we consider the definition of absolute value inequality ∣A∣>B |A| > B , which means A>B A > B or A<−B A < -B .

Thus, 2x−5>7 2x - 5 > 7 or 2x−5<−7 2x - 5 < -7 .

Let's solve these inequalities separately:

1. 2x−5>7 2x - 5 > 7

Add 5 to both sides:

2x>12 2x > 12

Divide by 2:

x>6 x > 6

2. 2x−5<−7 2x - 5 < -7

Add 5 to both sides:

2x<−2 2x < -2

Divide by 2:

x<−1 x < -1

Therefore, the solution is x<−1 or x>6 x < -1 \text{ or } x > 6 .

Answer

x<−1 or x>6 x < -1 \text{ or } x > 6

Exercise #17

Given:

∣3x−4∣≤5 \left|3x - 4\right| \leq 5

Which of the following statements is necessarily true?

Step-by-Step Solution

To solve ∣3x−4∣≤5 \left| 3x - 4 \right| \leq 5 , we should consider two scenarios for the absolute value: 3x−4≤5 3x - 4 \leq 5 and 3x−4≥−5 3x - 4 \geq -5 .

1. Solving 3x−4≤5 3x - 4 \leq 5 :

3x−4≤5 3x - 4 \leq 5

Add 4 to both sides:

3x≤9 3x \leq 9

Divide both sides by 3:

x≤3 x \leq 3

2. Solving 3x−4≥−5 3x - 4 \geq -5 :

3x−4≥−5 3x - 4 \geq -5

Add 4 to both sides:

3x≥−1 3x \geq -1

Divide both sides by 3:

x≥−13 x \geq -\frac{1}{3}

Combining both results, we have −13≤x≤3 -\frac{1}{3} \leq x \leq 3 , which is the correct answer.

Answer

−13≤x≤3 -\frac{1}{3} \leq x \leq 3

Exercise #18

Given:

∣2x+1∣>3 \left|2x + 1\right| > 3

Which of the following statements is necessarily true?

Step-by-Step Solution

To solve ∣2x+1∣>3 \left| 2x + 1 \right| > 3 , consider the two cases for the absolute value: 2x+1>3 2x + 1 > 3 and 2x+1<−3 2x + 1 < -3 .

1. Solving 2x+1>3 2x + 1 > 3 :

2x+1>3 2x + 1 > 3

Subtract 1 from both sides:

2x>2 2x > 2

Divide both sides by 2:

x>1 x > 1

2. Solving 2x+1<−3 2x + 1 < -3 :

2x+1<−3 2x + 1 < -3

Subtract 1 from both sides:

2x<−4 2x < -4

Divide both sides by 2:

x<−2 x < -2

Thus, the solution isx<−2 or x>1 x < -2 \text{ or } x > 1 .

Answer

x<−2 or x>1 x < -2 \text{ or } x > 1

Exercise #19

Given:

∣5x+3∣≤7 \left|5x + 3\right| \leq 7

Which of the following statements is necessarily true?

Step-by-Step Solution

To solve ∣5x+3∣≤7 \left| 5x + 3 \right| \leq 7 , consider both cases:5x+3≤7 5x + 3 \leq 7 and 5x+3≥−7 5x + 3 \geq -7 .

1. Solving 5x+3≤7 5x + 3 \leq 7 :

5x+3≤7 5x + 3 \leq 7

Subtract 3 from both sides:

5x≤4 5x \leq 4

Divide both sides by 5:

x≤0.8 x \leq 0.8

2. Solving 5x+3≥−7 5x + 3 \geq -7 :

5x+3≥−7 5x + 3 \geq -7

Subtract 3 from both sides:

5x≥−10 5x \geq -10

Divide both sides by 5:

x≥−2 x \geq -2

Combining both results, we find −2≤x≤0.8 -2 \leq x \leq 0.8 .

Answer

−2≤x≤0.8 -2 \leq x \leq 0.8

Exercise #20

Given:

∣3x−1∣<5x \left|3x - 1\right| < 5x

Which of the following statements is necessarily true?

Step-by-Step Solution

Let's solve the inequality ∣3x−1∣<5x \left|3x - 1\right| < 5x :

  1. Remove the absolute value by considering two cases:

    1. 3x−1<5x 3x - 1 < 5x
      Solve for x x :

    2. 3x−1<5x 3x - 1 < 5x

      Subtract 3x 3x from both sides:
      −1<2x -1 < 2x

      Divide both sides by 2 2 :
      −12<x -\frac{1}{2} < x

      Rewriting this inequality yields: x>−12 x > -\frac{1}{2}

    3. −(3x−1)<5x -(3x - 1) < 5x
      Simplifying yields:

    4. −3x+1<5x -3x + 1 < 5x

      Add 3x 3x to both sides:
      1<8x 1 < 8x

      Divide both sides by 8 8 :
      18<x \frac{1}{8} < x

      This implies x>18 x > \frac{1}{8}

  2. Combine results:

  3. Both conditions imply x>18 x > \frac{1}{8} . Thus, the solution is x>18 x > \frac{1}{8} .

Answer

x>18 x > \frac{1}{8}