Question Details

3. All the values of x satisfying the inequality

1 x + 5 1 2 x - 3

are

Options

A

  x< - 5  or  3 2 < x           6

B

  - 5 < x < 3 2  or  x > 3 2

C

  x < - 5  or  x > 3 2

D

  x< - 5  or  3 2 < x 8

Show Answer

Correct Answer :

Option C

  x < - 5  or  x > 3 2

Solution :

The correct option is:
x < - 5 or x > 3 2

Step-by-Step Explanation:

We are given the rational inequality:
1 x + 5 1 2x - 3
Below, we analyze this inequality step-by-step, referencing the method displayed in the provided image.

Step 1: Finding the Domain Constraints
The denominators of the fractions must not be equal to zero. As shown in Step 1 of the image:
x + 5 0 and 2 x - 3 0
Solving these constraints gives:
x - 5 and x 3 2

Step 2: Sign Analysis of the Denominators
To safely solve or cross-multiply, we must determine the sign of the denominators. In Step 2 of the image, the product of the two linear terms is analyzed under:
( x + 5 ) ( 2 x - 3 ) 0
Expanding this quadratic expression:
2 x 2 - 3x + 10x - 15 0
Simplifying:
2 x 2 + 7x - 15 0

Step 3: Finding the Roots of the Quadratic Equation
As shown in Step 3 of the image, we solve the quadratic equation:
2 x 2 + 7x - 15 = 0
Using the quadratic formula:
x = - 7 ± 7 2 - 4 ( 2 ) ( - 15 ) 2 ( 2 )
x = - 7± 49 + 120 4
x = - 7± 169 4
x = - 7± 13 4
This gives the two roots:
x 1 = - 7+ 13 4 = 6 4 = 3 2
x 2 = - 7- 13 4 = - 20 4 = - 5

Step 4: Testing Intervals
As specified in Step 4 of the image, we test the signs of the quadratic expression in the intervals determined by these roots:
1) For x < - 5 : both factors ( x + 5 ) and ( 2 x - 3 ) are negative, meaning their product is positive: ( x + 5 ) ( 2 x - 3 ) > 0 .
2) For - 5< x < 3 2 : the factor ( x + 5 ) is positive and ( 2 x - 3 ) is negative, meaning their product is negative: ( x + 5 ) ( 2 x - 3 ) < 0 .
3) For x > 3 2 : both factors ( x + 5 ) and ( 2 x - 3 ) are positive, meaning their product is positive: ( x + 5 ) ( 2 x - 3) > 0 .

Therefore, the inequality holds for the intervals where the denominators share the same sign:
x < - 5 or x > 3 2

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