Question Details

1 4 | x - 2 | dx is equal to

Options

A

5

B

7 2

C

3 2

D

5 2

Show Answer

Correct Answer :

Option D

5 2

Solution :

The correct option is:
5 2

Step-by-Step Explanation:

We are required to evaluate the definite integral:
I = 1 4 | x 2 | d x

First, let us analyze the behavior of the integrand, which contains an absolute value term |x2|. By definition, the absolute value function is defined as:
| x 2 | = { x 2 if  x 2 ( x 2 ) = 2 x if  x < 2

The interval of integration is from 1 to 4. Since the definition of the integrand changes at x=2, we can split the integration interval [1,4] into two sub-intervals: [1,2] and [2,4]. This allows us to write:
I = 1 2 | x 2 | d x + 2 4 | x 2 | d x

Substituting the corresponding expressions for the absolute value in each interval:
I = 1 2 ( 2 x ) d x + 2 4 ( x 2 ) d x

Now, let us evaluate each integral separately.

Part 1: Evaluating the first integral
I 1 = 1 2 ( 2 x ) d x
Using the power rule for integration, we get:
I 1 = [ 2 x x 2 2 ] 1 2
Applying the upper and lower limits:
I 1 = ( 2 ( 2 ) 2 2 2 ) ( 2 ( 1 ) 1 2 2 )
Simplifying terms:
I 1 = ( 4 2 ) ( 2 1 2 )
I 1 = 2 3 2 = 1 2

Part 2: Evaluating the second integral
I 2 = 2 4 ( x 2 ) d x
Integrating the terms:
I 2 = [ x 2 2 2 x ] 2 4
Applying the upper and lower limits:
I 2 = ( 4 2 2 2 ( 4 ) ) ( 2 2 2 2 ( 2 ) )
Simplifying terms:
I 2 = ( 8 8 ) ( 2 4 )
I 2 = 0 ( 2 ) = 2

Summing the parts:
Combining the values of both integrals to find the final value of I:
I = I 1 + I 2
I = 1 2 + 2 = 5 2

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