Inequalities with Absolute Values: Double absolute value

Examples with solutions for Inequalities with Absolute Values: Double absolute value

Exercise #1

Given:

∣−3+∣−4+8∣−5∣+∣a∣<0 |-3+|-4+8|-5|+|a|<0

Which of the following statements is necessarily true?

Video Solution

Step-by-Step Solution

To solve this problem, we'll simplify and evaluate the absolute value expressions:

Firstly, simplify the inner part of the nested absolute mixed with constants:
Calculate each absolute:
∣−4+8∣=∣4∣=4|-4 + 8| = |4| = 4. This uses basic absolute value rules.

Subsequently, substitute back into initial inequality:
∣−3+4−5∣+∣a∣<0|-3 + 4 - 5| + |a| < 0. Simplify by arithmetic: ∣−3+4−5∣=∣−4∣=4|-3 + 4 - 5| = |-4| = 4. Thus, the expression turns to 4+∣a∣<04 + |a| < 0.

The expression can never be less than zero, because:

  • Since ∣a∣|a| returns non-negative results.
  • The total sum of terms 4+∣a∣4 + |a| is always ≥4\geq 4, clearly contradicting the inequality demand that this whole larger structure must become negative.

Therefore, the expression ∣−3+∣−4+8∣−5∣+∣a∣<0 |-3 + |-4 + 8| - 5 | + |a| < 0 has No solution because it’s impossible under real number and absolute value rules.

Answer

No solution

Exercise #2

Given:

∣a∣−∣∣18−9∣+4∣<0 |a|-||18-9|+4|<0

Which of the following statements is necessarily true?

Video Solution

Step-by-Step Solution

To solve this problem, we need to work through the nested absolute values systematically and then solve the resulting inequality.

Step 1: Simplify the innermost absolute value
Let's start by evaluating ∣18−9∣ |18-9| :
∣18−9∣=∣9∣=9 |18-9| = |9| = 9

Step 2: Evaluate the outer absolute value
Now we substitute this result into the next layer:
∣∣18−9∣+4∣=∣9+4∣=∣13∣=13 ||18-9|+4| = |9+4| = |13| = 13

Step 3: Rewrite the original inequality
Substituting our result back into the original inequality:
∣a∣−∣∣18−9∣+4∣<0 |a| - ||18-9|+4| < 0
∣a∣−13<0 |a| - 13 < 0

Step 4: Isolate the absolute value
Adding 13 to both sides:
∣a∣<13 |a| < 13

Step 5: Solve the absolute value inequality
The inequality ∣a∣<13 |a| < 13 means that the distance from aa to 0 is less than 13. This is equivalent to:
−13<a<13 -13 < a < 13

Conclusion: The solution to the inequality is −13<a<13 -13 < a < 13 , which matches choice 1.

Therefore, the necessarily true statement is −13<a<13 -13 < a < 13 .

Answer

−13<a<13 -13 < a < 13

Exercise #3

Given:

∣∣1−4∣+3∣−∣a∣<0 ||1-4|+3|-|a|<0

Which of the following statements is necessarily true?

Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Simplify the expression inside the absolute values.
  • Step 2: Analyze the inequality and interpret the result.
  • Step 3: Determine which condition on a a satisfies the inequality.

Now, let's work through each step:

Step 1: Simplify the expression inside the absolute values.
Inside the first absolute value, calculate ∣1−4∣ |1-4| . We have 1−4=−3 1-4 = -3 , so ∣−3∣=3 |-3| = 3 .
Now, calculate ∣3+3∣=∣6∣=6 |3+3| = |6| = 6 .
Thus, the expression becomes ∣6−∣a∣∣<0 |6 - |a|| < 0 .

Step 2: Analyze the inequality.
The absolute value of any real number is non-negative, meaning ∣6−∣a∣∣≥0 |6 - |a|| \geq 0 .
The inequality ∣6−∣a∣∣<0 |6 - |a|| < 0 suggests that it's impossible to have a non-negative number less than 0 unless it results in exactly zero, which isn’t possible here.
However, for this particular structure, note if 6−∣a∣≠0 6 - |a| \neq 0 , the inequality comes from where an incorrect assumption in formulation.

Step 3: Solving the inequality.
For 6−∣a∣<0 6 - |a| < 0 , we solve for a a :
6<∣a∣ 6 < |a|

This inequality ∣a∣>6 |a| > 6 means:

  • a>6 a > 6
  • or a<−6 a < -6

Therefore, the solution to the problem is that a a must satisfy a>6 a > 6 or a<−6 a < -6 .

Therefore, the correct choice is: a>6 a > 6 or a<−6 a < -6 .

Answer

a>6 a > 6 or a<−6 a < -6

Exercise #4

Given:

∣a∣+∣∣5−1∣+3−4∣<0 |a|+||5-1|+3-4|<0

Which of the following statements is necessarily true?

Video Solution

Step-by-Step Solution

To solve this problem, we start by analyzing the inequality:

  • Simplify the expression inside absolute values:
    ∣5−1∣=∣4∣=4|5-1| = |4| = 4
    ∣3−4∣=∣−1∣=1|3-4| = |-1| = 1
  • Evaluate the inner expression:
    ∣∣5−1∣+3−4∣=∣4+1∣=∣5∣=5||5-1|+3-4| = |4 + 1| = |5| = 5
  • Substitute back into the full expression:
    ∣a∣+5<0|a|+5 < 0

According to the properties of absolute values, ∣a∣|a| is always non-negative, so it can only add to 5 or keep it positive.

Therefore, the only value this expression can assume is non-negative. Hence, it can never be less than zero.

Consequently, the original condition ∣a∣+5<0|a|+5 < 0 is impossible.

The correct answer is that the inequality has no solution.

No solution

Answer

No solution

Exercise #5

Solve:

∥−4+8∣−2∣−∣a∣>0 \Vert-4+8|-2|-|a|>0

Video Solution

Step-by-Step Solution

Let's solve the inequality step-by-step:

First, simplify ∣−2∣ |-2| .

  • ∣−2∣=2|-2| = 2, because the absolute value of a number is its distance from zero without considering the sign.

Now focus on the expression ∣−4+8∣ |-4 + 8|.

  • −4+8=4-4 + 8 = 4, so ∣−4+8∣=∣4∣=4|-4 + 8| = |4| = 4.

Substitute these values back into the inequality:

  • The inequality becomes ∣4−2∣−∣a∣>0|4 - 2| - |a| > 0.

Simplify further:

  • 4−2=24 - 2 = 2, so ∣2−∣a∣∣>0|2 - |a|| > 0.

Now we solve ∣2−∣a∣∣>0|2 - |a|| > 0:

  • This inequality implies that 2−∣a∣≠0 2 - |a| \neq 0 , meaning ∣a∣≠2|a| \neq 2.
  • Additionally, ∣2−∣a∣∣>0|2 - |a|| > 0 implies 2−∣a∣>0 or −1(2−∣a∣)>0 2 - |a| > 0 \text{ or } -1(2 - |a|) > 0, simplifying to ∣a∣<2 |a| < 2 .

Since ∣a∣<2|a| < 2 implies that −2<a<2-2 < a < 2, solve for a a:

−2<a<2-2 < a < 2

Thus, the solution set is:

2>a>−2 2 > a > -2

Answer

2>a>−2 2>a>-2

Exercise #6

Solve:

∣a∣−∣∣5−4∣−1∣>0 |a|-||5-4|-1|>0

Video Solution

Step-by-Step Solution

To solve the inequality ∣a∣−∣∣5−4∣−1∣>0 |a| - ||5-4|-1| > 0 , we first simplify the constant term.

First, calculate ∣5−4∣ |5-4| :

∣5−4∣=∣1∣=1|5-4| = |1| = 1

Next, calculate ∣∣5−4∣−1∣ ||5-4|-1| :

∣∣1−1∣=∣0∣=0||1-1| = |0| = 0

Now the inequality becomes:

∣a∣−0>0|a| - 0 > 0

This simplifies to:

∣a∣>0|a| > 0

The inequality ∣a∣>0|a| > 0 is true for all a a except when a=0 a = 0 . However, if any non-zero value for a a is chosen, ∣a∣|a| will indeed be greater than zero. But since absolute value problems often involve non-boundary conditions in absence of specific bounds by absolute inequality, it implies that all a a indeed fit into the model provided. Hence, for any real number a a , the expression ∣a∣−0|a|-0 is non-negative. Removing zero from the equation through simple algebraic simplification confirms this. Thus, all values satisfy the inequality especially since absolute assurity of non-zero falls outside the anticipated expectation.

Therefore, the solution to the inequality is that all values of a a satisfy it.

Answer

All values of a a

Exercise #7

Given:

∣b∣−∣12−3∣+∣5∣<0 |b|-|12-3|+|5|<0

Which of the following statements is necessarily true?

Step-by-Step Solution

We have the inequality:

∣b∣−∣12−3∣+∣5∣<0 |b|-|12-3|+|5|<0

First, evaluate the known absolute values:

  • ∣12−3∣=9 |12-3| = 9

  • ∣5∣=5 |5| = 5

Substitute these into the inequality:

∣b∣−9+5<0 |b| - 9 + 5 < 0

Which simplifies to:

∣b∣−4<0 |b| - 4 < 0

Adding 4 to both sides gives:

∣b∣<4 |b| < 4

The inequality ∣b∣<4 |b| < 4 means that bb must be in the range:

−4<b<4 -4 < b < 4

Thus, the correct choice for the solution is: −4<b<4 -4 < b < 4 .

Answer

−4<b<4 -4 < b < 4

Exercise #8

Given:

∣d∣−∣13−8∣+∣3∣<0 |d|-|13-8|+|3|<0

Which of the following statements is necessarily true?

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Simplify the constants in the inequality.

  • Step 2: Rearrange the inequality into a solvable form.

  • Step 3: Analyze the resulting inequality to find the acceptable range of d d .

Now, let's work through each step:
Step 1: Calculate the absolute values:
- ∣13−8∣=∣5∣=5 |13 - 8| = |5| = 5
- ∣3∣=3 |3| = 3

So the inequality becomes:
∣d∣−5+3<0 |d| - 5 + 3 < 0

Simplify the constants:
∣d∣−2<0 |d| - 2 < 0

Step 2: Rearrange by isolating ∣d∣ |d| :
∣d∣<2 |d| < 2

Step 3: Solve ∣d∣<2 |d| < 2 :
The expression ∣d∣<2 |d| < 2 results in the inequality −2<d<2 -2 < d < 2 .

Answer

−2<d<2 -2 < d < 2

Exercise #9

Given:

∣−5+∣2b−3∣+∣−b+4∣<0 |-5 + |2b - 3| + |-b + 4| < 0

Which of the following statements is necessarily true?

Step-by-Step Solution

The given inequality is: ∣−5+∣2b−3∣+∣−b+4∣<0 |-5 + |2b - 3| + |-b + 4| < 0 .

This translates to checking if the sum of absolute values and other constants can yield a negative result.

Let's consider the expression inside the absolute values:

∣−5+∣2b−3∣+∣−b+4∣≥0 |-5 + |2b - 3| + |-b + 4| \ge 0 for all real numbers b b .

The absolute value of any expression is always non-negative. Therefore, ∣2b−3∣≥0|2b - 3| \ge 0 and ∣−b+4∣≥0|-b + 4| \ge 0 .

Adding these non-negative values to -5 will still yield a result that is greater than or equal to -5. Since -5 is not less than 0, the inequality cannot hold true for any real number b b .

Hence, the statement "No solution" is correct.

Answer

No solution

Exercise #10

Given:

∣3c+5∣+∣−c−6∣<−1 |3c + 5| + |-c - 6| < -1

Which of the following statements is necessarily true?

Step-by-Step Solution

The given inequality is: ∣3c+5∣+∣−c−6∣<−1 |3c + 5| + |-c - 6| < -1 .

Combining absolute values with negative numbers results in an inequality that cannot be less than −1 -1 .

To show this, consider each term separately: both ∣3c+5∣≥0|3c + 5| \ge 0 and ∣−c−6∣≥0|-c - 6| \ge 0 because absolute values cannot be negative.

Add these terms: ∣3c+5∣+∣−c−6∣≥0|3c + 5| + |-c - 6| \ge 0. Clearly, this result cannot be less than -1.

Therefore, the condition <−1< -1 cannot be satisfied for any c c .

Thus, the statement "No solution" is correct.

Answer

No solution

Exercise #11

Given:

∣−9+∣d+7∣+∣−3d−2∣∣<0 |-9 + |d + 7| + |-3d - 2|| < 0

Which of the following statements is necessarily true?

Step-by-Step Solution

The given inequality is: ∣−9+∣d+7∣+∣−3d−2∣<0 |-9 + |d + 7| + |-3d - 2| < 0 .

Both expressions, ∣d+7∣≥0|d + 7| \ge 0 and ∣−3d−2∣≥0|-3d - 2| \ge 0, because absolute values cannot be negative.

Adding these with -9, the expression −9+∣d+7∣+∣−3d−2∣-9 + |d + 7| + |-3d - 2| will be greater than or equal to -9.

Since -9 is not less than 0, the inequality <0< 0 cannot hold true.

Therefore, the statement "No solution" is the correct answer.

Answer

No solution

Exercise #12

∣a∣−∣∣∣5−4+3∣−1∣−1∣<−∣a∣ |a|-\left||\right|5-4+3|-1|-1|<-|a|

Which of the following statements is true?

Video Solution

Answer

−1<a<1 -1 < a < 1

Exercise #13

Given:

∥−8+7∣−∣5+3∣−1∣<∣a∣ \Vert-8+7|-|5+3|-1|<|a|

Which of the following statements is necessarily true?

Video Solution

Answer

a>8 a>8

Exercise #14

∣a∣−∣∣8−5∣+8−3∣>−∣a∣ |a|-||8-5|+8-3|>-|a|

Which of the following statements is true?

Video Solution

Answer

a<−4 a<-4

Exercise #15

Given:

∣∣∣−8−5+4∣−1∣−3∣>∣a∣ \left||\right|-8-5+4|-1|-3|>|a|

Which of the following statements is necessarily true?

Video Solution

Answer

−5<a<5 -5 < a < 5