Absolute Values: Functions, Properties

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The distance between a number and the origin of a number line is known as its absolute value. It's denoted by the symbol |a|, which stands for the magnitude of any integer 'a'. Regardless of the sign, the absolute value of any integer, positive or negative, will be the real numbers. The modulus of an is represented by two vertical lines |a|, which is also known as the modulus of a. Absolute value of x is the distance between x and zero, indicated by "| x |" (and interpreted as "the absolute value of x"). This is why absolute value can never be negative; it just asks "how far?" rather than "in which direction?" This indicates that | 3 | = 3 not just because 3 is three units to the right of zero, but also because | –3 | is three units to the left of zero.

Key Terms: Absolute Values, Number, Graph, Function, Distance, 

Also read: Isosceles Triangle Theorems


Absolute Value of a Number

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In a number line, the absolute value of a number or integer is the number's actual distance from zero. As a result, the absolute value is always a positive number, never a negative one.

Absolute values can be defined in the following way:

{ a if a 0}

If a < 0, then |a| = -a

Note that 0 has no absolute value since absolute value transforms the sign of the integers from negative to positive, while zero has no sign.

If the number is positive, just a positive number will be returned. And if the number is negative, the modulus of that number will be positive as well. It is represented by the symbol |n|, where n is an integer.

Also read: Calculus Formula


Absolute Value Function

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f(x) = |x| is the absolute value function, which means:

  • |x| = +x for x > 0
  • |x| = -x for x < 0

Also read: Differentiation and Integration Formula


Absolute Value Properties

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Property

Expression

Non-negativity

| x | ≥ 0

Positive-definiteness

| x | = 0 ↔ a = 0

Multiplicatively

| x × y| = |x| × |y|

Subadditivity

| x + y| ≤ | x | + | y |

Symmetry 

|-x| = |x|

Identity of indiscernible 

(equivalent to positive definiteness)

| x – y | = 0 ↔ a = b

Triangle inequality (equivalent 

to subadditivity)

| x – y | ≤ | x – z | + | z – x |

Preservation of division 

(equivalent to multiplicatively)

| x / y| = | x | / | y |

Equivalent to subadditivity

| x – y | ≥ | | x | – | y | |


Absolute Value of a Real Number

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The absolute value of a real number x will satisfy the following conditions.

If x ≥ 0, | x | = x.

If x < 0, | x | = – x

Looking at the absolute value of 2 in the graph below. The distance of 2 from 0 is represented by |2|. As a result, both +2 and -2 are the same distance from the origin. However, because distance is never calculated in the negative, it would be accepted as 2.

Absolute Value of a Real Number

Absolute Value of a Real Number


Absolute Value of Complex Number

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Real numbers with imaginary numbers make up complex numbers. As a result, unlike integers, finding the absolute value for them is challenging. Assume that the supplied complex number is  x+iy.

z = x+iy

z will have the following absolute value:

|z|=\(\sqrt{ [Re(z)2+lm(z)2]}\)

\(\sqrt{(x^2+y^2)}\) = |z|

Here,the real numbers x and y are used.

Also read: Difference between Sequence and Series


Absolute Value in Number Line

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Absolute value graph is a graph of absolute values. Because the absolute value of any real number is always positive, the absolute value of any number or function graph will always be positive.

Graph the absolute value of the number -9 as an example. 

Solution: |-9| has an absolute value of +9.

As a result, the graph with the absolute value of -9 will appear as follows.

Absolute Value in Number Line

Absolute Value in Number Line


Things to Remember

  1. The term "absolute value" refers to the removal of any negative sign from a number and the treatment of all numbers as positive (or zero).
  2. In a number line, the absolute value of any integer or number represents the number's distance from zero.
  3. Absolute value is represented by the symbol |x|, where x is an integer.
  4. |x| is pronounced 'mod x' or 'modulus of x.'
  5. The absolute value of an integer on the number line represents its distance from zero without taking direction into account. The absolute value of an integer is never negative.

Also read: First Order Differential Equation


Sample Questions

Ques. Arrange the numbers in ascending order. -|-14|, |12|, |7|, |-91|, |-5|, |-8|, |-65|, |6| [2 marks]

Ans. Finding the absolute values of the given numbers first.

-14, 12, 7, 91, 5, 8, 65, 6

Place the numbers in ascending order now (smallest to the largest number)

-14, 5, 6, 7, 8, 12, 65, 91

Ques. If there are any, find the x-intercept(s) of the graph of the function f(x)=|4x+B|8 in terms of B. [3 marks]

Ans. Make f(x)=0. and find the value of x:

f(x)=0

|4x+B|−8=0

|4x+B|=8

Rewrite the following equation as a compound equation and solve each portion separately:

4x + B=8 or 4x + B= 8

4x+B= −8

4x+B−B= −B−8

4x= −B−8

4x÷4= (−B−8)÷4

x= −B−84/4

4x+B= 8

4x+B−B=−B+8

4x=−B+8

4x÷4=(−B+8)÷4

x= −B+84/4

Ques. A number's absolute value is ten less than its own. What is this number, exactly? [3 marks]

Ans. This can be rewritten as an equation with N as the variable:

N=|N|10

Because a nonnegative number equals its own absolute value, this number must be negative.

|N|=N, and we may rewrite the equation as

N= -N-10

N+N=-N-10+N

2N=-10

2N/2=-10/2

N=-5

The only number that meets the condition is -5.

Ques. Which of the following has the highest absolute value if 1n0? [2 marks]
(1) n+1
(2) n/2 
(3) n2
(4) 1/n2
(5) 1/n

Ans. |1/n2|

We know the following since -1 < n < 0:

0 < n2  < 1;

-1 < n/2 < 0;

1/n2 > 1;

1/n < -1;

0 < n+1 < 1.

Furthermore, we must compare absolute numbers, therefore the greatest must be either |1/n2| or |1/n|.

We also know that when -1 < n < 0, |n2| < |n|.

As a result, we can be certain that |1/n2| >|1/n|.

Ques. When do we use Absolute Values When Solving Radicals? [2 marks]

Ans. Radicals are real numbers that can be represented as powers with rational exponents.

X\(\sqrt{n}\)= n1/x.

If the radical is an even-root radical,

\(\sqrt{x}\) or 4 \(\sqrt{x}\) then the value under the radical has to be positive i.e. x > 0

Hence \(\sqrt{x^2}\) = |x|, because an even-root radical is a positive quantity, as the absolute value. Hence, we use absolute values while solving even-root radicals.

The absolute value symbol is not needed if the radical is an odd-root radical as the value under an odd root radical can be positive or negative.

3\(\sqrt{-8}\) = -2 and 3\(\sqrt{8}\) = 2

Ques. What is an Absolute Value's One Basic Rule? [2 marks]

Ans. The fundamental rule of absolute value is that any number's absolute value is always positive. If the number is a positive integer, it has a positive absolute value, such as |15| = 15. Even though the number is a negative integer, the absolute value is positive, as shown by |-20| = 20.'

Ques. Ria's tutor instructs her to use the definition of the absolute function to solve the following absolute value equation. |x-2| equals 4. Is it possible for us to assist her? [3 marks]

Ans. |x-2|=4 is the given equation. When we eliminate the absolute value sign on one side of the equation, we have the definition of the absolute value function. On the other hand, we obtain a + symbol. + 4 x-2= This yields two equations, each of which we must solve separately.

x - 2 = +4 

x = +4 + 2

x = +6

x - 2 = -4

x = -4 + 2 

x = -2 

So, the following equation's answers are x = 6, x = -2.

Ques. Mohan is looking for the values of the following variables. Should we assist her in applying the definition of absolute value? (I) |-13/5|, (II) - | -3|, and (III) |2(-3) +4|. [2 marks]

Ans. We know absolute value always results in non-negative quantities. As a result, we have the following options.

(I) | -13/15| = 13/15 

(II). - |-3| = -(3) = -3 

(III). |2(-3) + 4| = |-6+4| = |-2| = 2

As a result, (I) | -13/15| = 13/15, (II) | -3 | = -3, and (III) |2(-3) + 4| = 2

Ques. Calculate the absolute maximum and minimum values of f(x) = \(\frac{x}{x^2+x+1}\) on the interval [-2, 0] [4 marks]

Ans. Calculating critical numbers.

f'(x) = \(\frac{x^2+x+1-x(2x+1)}{(x^2+x+1)^2}\)

-  \(\frac{x^2+1}{(x^2+x+1)^2}\)

Therefore,

f'(x) = – \(\frac{x^2+1}{(x^2+x+1)^2}\)

Making f’(x) = 0, – x+ 1 = 0 ⇒ x = – 1 or x = 1

So the critical numbers are x = -1 and x = 1

x = 1 ∈ [-2, 0] discarded for the study of absolute extremes.

Now Calculating the absolute extremes, 

At the crucial value x=-1 and the interval's extremes, we evaluate the function.

The absolute maximum is the highest value, and the absolute minimum is the lowest.

We have

f(-2) = –\(\frac{2}{3} \approx\) - 0.67

f(-1) = -1

f(0) = 0.

As a result, the absolute maximum is 0 and occurs at x = 0, while the absolute minimum is -1 and occurs at x=-1.

Ques. Find all real solutions with absolute value to the equation. 2|-2x - 2| - 3 = 13 [3 marks]

Ans. 2 | - 2 x - 2| = 16, 

| - 2 x - 2| = 8 | 

The expression - 2 x - 2 equals 8 or - 8 is identical to stating the preceding equation.

  1. a) -2 x - 2 = 8

x = - 5 

  1. b) - 2 x - 2 = - 8

x = 3 

Check that x = - 5 and x = 3 are solutions to the above problem by substituting them.

Set of solutions: {-5,3}

Also Read:

CBSE CLASS XII Related Questions

  • 1.
    Find:

    The principal value of \[ \sec^{-1}(\sqrt{2})+2\csc^{-1}(-2) \] is:

      • \(-\frac{\pi}{2}\)
      • \(-\frac{\pi}{4}\)
      • \(\frac{\pi}{4}\)
      • \(\frac{\pi}{2}\)

    • 2.
      Find:

      If \[ (3\hat{i}-2\hat{j}+5\hat{k})\times(4\hat{i}+p\hat{j}+q\hat{k})=\vec{0} \] then find the values of \(p\) and \(q\).

        • \(p = -\frac{2}{3}, \, q = \frac{5}{3}\)
        • \(p = -\frac{8}{3}, \, q = \frac{20}{3}\)
        • \(p = \frac{20}{3}, \, q = -\frac{8}{3}\)
        • \(p = 0, \, q = 0\)

      • 3.

        An NGO organises a charity event in which they decide to distribute woollen caps to protect children from winter. The caps to be distributed are in three separate boxes, Box I has 30 red caps, Box II has 20 red and 10 green caps, and Box III has 30 green caps. The probability that a Box i is selected and a cap picked out is i/6, where i = 1, 2, 3.  
        Based on the above information, answer the following questions :


          • 4.
            Find a point on the line \( \frac{x - 2}{3} = \frac{1 - y}{2} = \frac{z - 3}{2} \) at a distance of \( \sqrt{2} \) units from the point \( (1, 2, 3) \).


              • 5.

                A carpenter needs to design a wooden box in the shape of a cuboid such that the sum of its length and breadth is 3 cm more than its height. Twice of its length, thrice of its breadth and its height add up to 10 cm. Its breadth added to 7 times its height is 1 cm less than 3 times its length. 


                  • 6.

                    At a birthday party, children are being served orange juice in conical cups, as shown in the figure. 


                    Each cup is 15 cm deep and has a radius 5 cm. The juice is being poured into this cup at a rate of 0·1 cm3/s.
                    On the basis of the above information, answer the following questions :

                      CBSE CLASS XII Previous Year Papers

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