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All questions of Quadratic Equations for SSC CGL Exam

Directions: In each of these questions, two equations (I) and (II) are given. You have to solve both the equations and give answer.
I. x2 – 16x + 55 = 0
II. y2 + y – 30 = 0
  • a)
    if x > y
  • b)
    if x ≤ y 
  • c)
    if x ≥ y
  • d)
    if x < y
Correct answer is option 'C'. Can you explain this answer?

Krish Iyer answered
Solving the Equations
To determine the relationship between x and y, we first need to solve both equations provided.
Equation I: x² - 16x + 55 = 0
1. Using the quadratic formula:
The roots are calculated using the formula x = [-b ± √(b² - 4ac)] / 2a, where a = 1, b = -16, and c = 55.
2. Calculating the discriminant:
Discriminant (D) = b² - 4ac = (-16)² - 4(1)(55) = 256 - 220 = 36.
3. Finding the roots:
x = [16 ± √36] / 2
x = [16 ± 6] / 2
- x₁ = (16 + 6) / 2 = 22 / 2 = 11
- x₂ = (16 - 6) / 2 = 10 / 2 = 5
So, the solutions for x are 11 and 5.
Equation II: y² + y - 30 = 0
1. Using the quadratic formula:
Here, a = 1, b = 1, and c = -30.
2. Calculating the discriminant:
D = 1² - 4(1)(-30) = 1 + 120 = 121.
3. Finding the roots:
y = [-1 ± √121] / 2
y = [-1 ± 11] / 2
- y₁ = (10) / 2 = 5
- y₂ = (-12) / 2 = -6
So, the solutions for y are 5 and -6.
Comparing x and y
- The values of x are 11 and 5.
- The values of y are 5 and -6.
Relationship Analysis
- If we compare the maximum value of x (which is 11) to the maximum value of y (which is 5), we find:
- 11 > 5 (x > y)
- Now comparing the minimum values:
- 5 (x) ≥ -6 (y)
Thus, it can be concluded that:
Final Conclusion
The relationship is:
- x ≥ y, as the maximum x (11) is greater than the maximum y (5) and the minimum x (5) is also greater than the minimum y (-6).
Therefore, the correct answer is option 'C': if x ≥ y.

Directions: In each of these questions, two equations (I) and (II) are given. You have to solve both the equations and give answer.
I. 7x + 12y = 13 
II. 12x + 17y = 8
  • a)
    if x > y
  • b)
    if x ≤ y 
  • c)
    if x ≥ y
  • d)
    if x < y
Correct answer is option 'D'. Can you explain this answer?

Ssc Cgl answered
I. 7x + 12y = 13 
II. 12x + 17y = 8
→ I × 12 – II × 7
12y × 12 – 17y × 7 = 13 × 12 – 8 × 7
25y = 100
y = 4
7x + 12 × 4 = 13 
x = – 5 
Answer: x < y
Hence, Option D is correct.

Directions: In each of these questions, two equations (I) and (II) are given. You have to solve both the equations and give answer.
I. x2 + 31x + 168 = 0 
II. y2 + 5y – 14 = 0
  • a)
    if x > y
  • b)
    if x ≤ y 
  • c)
    if x ≥ y
  • d)
    if x < y
Correct answer is option 'B'. Can you explain this answer?

Tarun Nambiar answered
Solving the Equations
To determine the relationship between x and y, we need to solve both equations separately.
Equation I: x² + 31x + 168 = 0
1. Finding Roots:
- Use the quadratic formula: x = [-b ± √(b² - 4ac)] / 2a.
- Here, a = 1, b = 31, c = 168.
- Discriminant = b² - 4ac = 31² - 4(1)(168) = 961 - 672 = 289.
- Roots: x = [-31 ± √289] / 2 = [-31 ± 17] / 2.
2. Calculating the Roots:
- x₁ = (-31 + 17) / 2 = -14 / 2 = -7.
- x₂ = (-31 - 17) / 2 = -48 / 2 = -24.
Thus, the solutions for x are: x = -7 and x = -24.
Equation II: y² + 5y - 14 = 0
1. Finding Roots:
- Again use the quadratic formula: y = [-b ± √(b² - 4ac)] / 2a.
- Here, a = 1, b = 5, c = -14.
- Discriminant = b² - 4ac = 5² - 4(1)(-14) = 25 + 56 = 81.
- Roots: y = [-5 ± √81] / 2 = [-5 ± 9] / 2.
2. Calculating the Roots:
- y₁ = (-5 + 9) / 2 = 4 / 2 = 2.
- y₂ = (-5 - 9) / 2 = -14 / 2 = -7.
Thus, the solutions for y are: y = 2 and y = -7.
Comparing x and y
- Values of x: -7, -24.
- Values of y: 2, -7.
Analyzing Relationships
- Case 1: If x = -7 and y = 2, then x < y.="" -="">case="" 2:="" if="" x="-24" and="" y="-7," then="" x="">< y.="" in="" both="" cases,="" x="" is="" less="" than="" or="" equal="" to="" y.="">Final Conclusion
The correct answer is option 'B': if x ≤ y.

Directions: In each of these questions, two equations (I) and (II) are given. You have to solve both the equations and give answer.
I. x2 + 48x – 153 = 0
II. y2 = 32y – 156
  • a)
    if x > y
  • b)
    if x ≤ y 
  • c)
    if x ≥ y
  • d)
    if x < y
Correct answer is option 'D'. Can you explain this answer?

Iq Funda answered
I. x2 + 48x – 153 = 0
x2 + 51x – 3x – 153 = 0
x = – 51 and 3
II. y2 = 32y – 156
y2 – 32y + 156 = 0
y2 – 26y – 6x + 156 = 0
y = 26 and 6
Answer: x < y
Hence, Option D is correct.

Directions: In each of these questions, two equations (I) and (II) are given. You have to solve both the equations and give answer.
I. x3 – 9x2 + 18x = 0
II. y2 + 22y + 85 = 0
  • a)
    if x > y
  • b)
    if x ≤ y 
  • c)
    if x ≥ y
  • d)
    if x < y
Correct answer is option 'A'. Can you explain this answer?

I. x3 – 9x2 + 18x = 0
x(x2 – 9x + 18) = 0
x2 – 9x + 18 = 0
x2 – 6x – 3x + 18 = 0
x = 0, 6 and 3
II. y2 + 22y + 85 = 0
y2 + 17y + 5y + 85 = 0
y = – 17 and – 5
x > y
Hence, Option A is correct.

Directions: In each of these questions, two equations (I) and (II) are given. You have to solve both the equations and give answer.
I. x2 – 15 = 14x
II. 17y = – 14 – 3y2
  • a)
    if x > y
  • b)
    if x ≤ y 
  • c)
    if x ≥ y
  • d)
    if x < y
Correct answer is option 'C'. Can you explain this answer?

Aim It Academy answered
I. x2 – 15 = 14x
x2 – 14x – 15 = 0
x2 – 15x + x – 15 = 0
x = 15 and – 1
II. 17y = – 14 – 3y2
3y2 + 17y + 14 = 0
3y2 + 3y + 14y + 14 = 0 

Answer: x ≥ y
Hence, Option C is correct.

Directions: In each of these questions, two equations (I) and (II) are given. You have to solve both the equations and give answer.
I. 4x + 6y = 82 
II. 21x + 4y = 183
  • a)
    if x > y
  • b)
    if x ≤ y 
  • c)
    if x ≥ y
  • d)
    if x < y
Correct answer is option 'D'. Can you explain this answer?

I. 4x + 6y = 82 
II. 21x + 4y = 183
→ 1.50 × II – I
31.50x – 4x = 274.50 – 82
27.50x = 192.50
x = 7
Put the value of x = 7 in I
4 × 7 + 6y = 82 
28 + 6y = 82
6y = 54
y = 9
Answer: x < y
Hence, Option D is correct.

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