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Algebra

Quadratic Equations

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Quadratic Equations Score: 0/10
1. Solve for x :   3x 2 + 18x - 81 = 0

1. Solve for x :   3x 2 + 18x - 81 = 0

1. Solve for x :

    3x 2 + 18x - 81 = 0

A. x = 9   or   x = - 9
B. x = 3   or   x = - 9
C. x = 3   or   x = - 27
D. None of the above
2. Solve for x :   12x 2 - 11x + 2 = 0

2. Solve for x :   12x 2 - 11x + 2 = 0

2. Solve for x :

    12x 2 - 11x + 2 = 0

A. x = 4   or   x = 3 2
B. x = 1   or   x = 2
C. x = 1 4   or   x = 2 3
D. None of the above
3. Solve for x :   2x ( 3x + 5 ) = 11

3. Solve for x :   2x ( 3x + 5 ) = 11

3. Solve for x :

    2x ( 3x + 5 ) = 11

A. x = - 5 + 91 6    or    x = - 5 - 91 6
B. x = 5 + 91 6    or    x = 5 - 91 6
C. x = - 5   or   x = 5
D. None of the above
4. Solve for x by completing the square:  2x 2 + x - 8 = 0

4. Solve for x by completing the square:  2x 2 + x - 8 = 0

4. Solve for x by completing the square:

   2x 2 + x - 8 = 0

A. x = 1 + 65 4    or    x = 1 - 65 4
B. x = - 1 + 65 4    or    x = - 1 - 65 4
C. x = - 1   or   x = 1
D. None of the above
5. Solve for x by completing the square:  - 2x 2 - 2x +  2 3  = 0

5. Solve for x by completing the square:  - 2x 2 - 2x +  2 3  = 0

5. Solve for x by completing the square:

   - 2x 2 - 2x +  2 3  = 0

A. x = - 3 + 21 6    or    x = - 3 - 21 6
B. x = 3    or    x = - 3
C. x = 3 + 21 6    or    x = 3 - 21 6
D. None of the above
6. Solve for x by completing the square:  x 2 - 6x - 39 = 0

6. Solve for x by completing the square:  x 2 - 6x - 39 = 0

6. Solve for x by completing the square:

   x 2 - 6x - 39 = 0

A. x = - 3 + 4 3    or    x = - 3 - 4 3
B. x = 3 + 4 3    or    x = 3 - 4 3
C. x = 9    or    x = - 9
D. None of the above
7. Solve the following inequality :   5 ( x 2 - 1 ) ≤ 2 ( 19x - 13 )

7. Solve the following inequality :   5 ( x 2 - 1 ) ≤ 2 ( 19x - 13 )

7. Solve the following inequality :

    5 ( x 2 - 1 ) ≤ 2 ( 19x - 13 )

A. x ≤  3 5   or   x ≥ 7
B. 3 5  ≤ x ≤ 7
C. x ≥  3 5   or   x ≥ 7
D. None of the above
8. Solve the following inequality :   - 15x 2 + x + 40 ≤ 0

8. Solve the following inequality :   - 15x 2 + x + 40 ≤ 0

8. Solve the following inequality :

    - 15x 2 + x + 40 ≤ 0

A. - 5 3  ≤ x ≤  8 5
B. - 8 5  ≤ x ≤  5 3
C. x ≤ - 8 5   or   x ≥  5 3
D. None of the above
9. Solve the following inequality :   8x ( x + 1 ) ≥ 4 ( 9 - x )

9. Solve the following inequality :   8x ( x + 1 ) ≥ 4 ( 9 - x )

9. Solve the following inequality :

    8x ( x + 1 ) ≥ 4 ( 9 - x )

A. - 3 ≤ x ≤  3 2
B. - 3 ≥ x ≥  3 2
C. x ≤ - 3   or   x ≥  3 2
D. None of the above
10. Solve the following inequality :   5x ( 4x + 5 ) < 4 ( x - 1 )

10. Solve the following inequality :   5x ( 4x + 5 ) < 4 ( x - 1 )

10. Solve the following inequality :

    5x ( 4x + 5 ) < 4 ( x - 1 )

A. - 4 5  < x < - 1 4
B. 1 4  < x <  4 5
C. x < - 4 5   or   x > - 1 4
D. None of the above

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Solutions

Quadratic Equations Question 1 of 10
1. Solve for x :   3x 2 + 18x - 81 = 0

1. Solve for x :   3x 2 + 18x - 81 = 0

1. Solve for x :

    3x 2 + 18x - 81 = 0

A. x = 9   or   x = - 9
B. x = 3   or   x = - 9
C. x = 3   or   x = - 27
D. None of the above
Correct Answer
Option B
Detailed Solution

Solution Details

Given   3x 2 + 18x - 81 = 0

•   3x 2 + 18x - 81 =  x 2 + 6x - 27 = 0

•   ( x - 3 ) ( x + 9 ) = 0

•   ( x - 3 ) = 0   or   ( x + 9 ) = 0

∴   x = 3   or  x = - 9

For more info please see

Quadratic Equations

Quadratic Equations Question 2 of 10
2. Solve for x :   12x 2 - 11x + 2 = 0

2. Solve for x :   12x 2 - 11x + 2 = 0

2. Solve for x :

    12x 2 - 11x + 2 = 0

A. x = 4   or   x = 3 2
B. x = 1   or   x = 2
C. x = 1 4   or   x = 2 3
D. None of the above
Correct Answer
Option C
Detailed Solution

Solution Details

Given   12x 2 - 11x + 2 = 0

•   12x 2 - 11x + 2 = 0

•   ( 4x - 1 ) ( 3x - 2 ) = 0

•   ( 4x - 1 ) = 0   or   ( 3x - 2 ) = 0

∴   x =  1 4   or  x =  2 3

For more info please see

Quadratic Equations

Quadratic Equations Question 3 of 10
3. Solve for x :   2x ( 3x + 5 ) = 11

3. Solve for x :   2x ( 3x + 5 ) = 11

3. Solve for x :

    2x ( 3x + 5 ) = 11

A. x = - 5 + 91 6    or    x = - 5 - 91 6
B. x = 5 + 91 6    or    x = 5 - 91 6
C. x = - 5   or   x = 5
D. None of the above
Correct Answer
Option A
Detailed Solution

Solution Details

Given   2x ( 3x + 5 ) = 11

•   2x ( 3x + 5 ) = 11

•   6x 2 + 10x - 11 = 0

•   x  =  – b  ± b 2 – 4ac 2a       The equation cannot be factorised so we use the quadratic formula


•   x  =  – 10  ± ( 10 ) 2 – 4 ( 6 ) ( - 11 ) 2 ( 6 )   =   – 10  ± 364 12   =   – 10  ±  2 91 12   =   – 5  ± 91 6


∴   x =  – 5  + 91 6   or  x =  – 5  – 91 6

For more info please see

Quadratic Equations

Given   2x ( 3x + 5 ) = 11

•   2x ( 3x + 5 ) = 11

•   6x 2 + 10x - 11 = 0

•   x  =  – b  ± b 2 – 4ac 2a

The equation cannot be factorised so we use the quadratic formula


•   x  =  – 10  ± ( 10 ) 2 – 4 ( 6 ) ( - 11 ) 2 ( 6 )

   =   – 10  ± 364 12

   =   – 10  ±  2 91 12

   =   – 5  ± 91 6


∴   x =  – 5  + 91 6   or  x =  – 5  – 91 6

For more info please see

Quadratic Equations

Quadratic Equations Question 4 of 10
4. Solve for x by completing the square:  2x 2 + x - 8 = 0

4. Solve for x by completing the square:  2x 2 + x - 8 = 0

4. Solve for x by completing the square:

   2x 2 + x - 8 = 0

A. x = 1 + 65 4    or    x = 1 - 65 4
B. x = - 1 + 65 4    or    x = - 1 - 65 4
C. x = - 1   or   x = 1
D. None of the above
Correct Answer
Option B
Detailed Solution

Solution Details

Given   2x 2 + x - 8 = 0

•   2x 2 + x - 8 = 0

•   x 2 +  1 2 x - 4 = 0

•   x 2 +  1 2 x +  1 16  = 4 +  1 16

•   ( x +  1 4 ) 2  =  65 16

•   x +  1 4  = ±  65 4

•   x =  - 1 ± 65 4

∴   x =  - 1 + 65 4      or      x =  - 1 - 65 4

For more info please see

Quadratic Equations

Quadratic Equations Question 5 of 10
5. Solve for x by completing the square:  - 2x 2 - 2x +  2 3  = 0

5. Solve for x by completing the square:  - 2x 2 - 2x +  2 3  = 0

5. Solve for x by completing the square:

   - 2x 2 - 2x +  2 3  = 0

A. x = - 3 + 21 6    or    x = - 3 - 21 6
B. x = 3    or    x = - 3
C. x = 3 + 21 6    or    x = 3 - 21 6
D. None of the above
Correct Answer
Option A
Detailed Solution

Solution Details

Given  - 2x 2 - 2x +  2 3  = 0

•   - 2x 2 - 2x +  2 3  = 0

•   x 2 + x -  1 3  = 0

•   x 2 + x +  1 4  =  1 3  +  1 4

•   ( x +  1 2 ) 2  =  7 12

•   x +  1 2  = ±  7 12

•   x +  1 2  = ±  7 12 12 12

•   x +  1 2  = ±  84 12

•   x =  - 6 ± 4 × 21 12

∴   x =  - 3 + 21 6      or      x =  - 3 - 21 6

For more info please see

Quadratic Equations

Quadratic Equations Question 6 of 10
6. Solve for x by completing the square:  x 2 - 6x - 39 = 0

6. Solve for x by completing the square:  x 2 - 6x - 39 = 0

6. Solve for x by completing the square:

   x 2 - 6x - 39 = 0

A. x = - 3 + 4 3    or    x = - 3 - 4 3
B. x = 3 + 4 3    or    x = 3 - 4 3
C. x = 9    or    x = - 9
D. None of the above
Correct Answer
Option B
Detailed Solution

Solution Details

Given  x 2 - 6x - 39 = 0

•   x 2 - 6x - 39 = 0

•   x 2 - 6x + 9 = 39 + 9

•   ( x - 3 ) 2  = 48

•   x - 3 = ± 48

•   x = 3 ± 4 3

∴   x = 3 + 4 3      or      x = 3 - 4 3

For more info please see

Quadratic Equations

Quadratic Equations Question 7 of 10
7. Solve the following inequality :   5 ( x 2 - 1 ) ≤ 2 ( 19x - 13 )

7. Solve the following inequality :   5 ( x 2 - 1 ) ≤ 2 ( 19x - 13 )

7. Solve the following inequality :

    5 ( x 2 - 1 ) ≤ 2 ( 19x - 13 )

A. x ≤  3 5   or   x ≥ 7
B. 3 5  ≤ x ≤ 7
C. x ≥  3 5   or   x ≥ 7
D. None of the above
Correct Answer
Option B
Detailed Solution

Solution Details

Given  5 ( x 2 - 1 ) ≤ 2 ( 19x - 13 )

•   5 ( x 2 - 1 ) ≤ 2 ( 19x - 13 )

•   5x 2 - 5 ≤ 38x - 26

•   5x 2 - 38x + 21 ≤ 0

•   ( 5x - 3 ) ( x - 7 ) ≤ 0

•   5x 2 - 38x + 21 = 0  at  x = 3 5  and  x = 7
+0-0+

||||
| 3 5 7|
   We have to find values of x where 5x 2 - 38x + 21 ≤ 0.


∴    3 5  ≤  x  ≤  7

For more info please see

Quadratic Equations

Quadratic Equations Question 8 of 10
8. Solve the following inequality :   - 15x 2 + x + 40 ≤ 0

8. Solve the following inequality :   - 15x 2 + x + 40 ≤ 0

8. Solve the following inequality :

    - 15x 2 + x + 40 ≤ 0

A. - 5 3  ≤ x ≤  8 5
B. - 8 5  ≤ x ≤  5 3
C. x ≤ - 8 5   or   x ≥  5 3
D. None of the above
Correct Answer
Option C
Detailed Solution

Solution Details

Given  - 15x 2 + x + 40 ≤ 0

•   - 15x 2 + x + 40 ≤ 0

•   15x 2 - x - 40 ≥ 0

•   ( 3x - 5 ) ( 5x + 8 ) ≥ 0

•   15x 2 - x - 40 ≥ 0  at  x = 5 3  and  x = - 8 5
+0-0+

||||
|- 8 5 5 3 |
   We have to find values of x where 15x 2 - x - 40 ≥ 0.


∴    x ≤ - 8 5   or   x ≥  5 3

For more info please see

Quadratic Equations

Quadratic Equations Question 9 of 10
9. Solve the following inequality :   8x ( x + 1 ) ≥ 4 ( 9 - x )

9. Solve the following inequality :   8x ( x + 1 ) ≥ 4 ( 9 - x )

9. Solve the following inequality :

    8x ( x + 1 ) ≥ 4 ( 9 - x )

A. - 3 ≤ x ≤  3 2
B. - 3 ≥ x ≥  3 2
C. x ≤ - 3   or   x ≥  3 2
D. None of the above
Correct Answer
Option C
Detailed Solution

Solution Details

Given  8x ( x + 1 ) ≥ 4 ( 9 - x )

•   8x ( x + 1 ) ≥ 4 ( 9 - x )

•   8x 2 + 8x ≥ 36 - 4x

•   8x 2 + 12x - 36 ≥ 0

•   2x 2 + 3x - 9 ≥ 0

•   ( 2x - 3 ) ( x + 3 ) ≥ 0

•   2x 2 + 3x - 9 ≥ 0  at  x = 3 2  and  x = - 3
+0-0+

||||
|- 3 3 2 |
   We have to find values of x where 2x 2 + 3x - 9 ≥ 0.


∴    x ≤ - 3   or   x ≥  3 2

For more info please see

Quadratic Equations

Quadratic Equations Question 10 of 10
10. Solve the following inequality :   5x ( 4x + 5 ) < 4 ( x - 1 )

10. Solve the following inequality :   5x ( 4x + 5 ) < 4 ( x - 1 )

10. Solve the following inequality :

    5x ( 4x + 5 ) < 4 ( x - 1 )

A. - 4 5  < x < - 1 4
B. 1 4  < x <  4 5
C. x < - 4 5   or   x > - 1 4
D. None of the above
Correct Answer
Option A
Detailed Solution

Solution Details

Given  5x ( 4x + 5 ) < 4 ( x - 1 )

•   5x ( 4x + 5 ) < 4 ( x - 1 )

•   20x 2 + 25x < 4x - 4

•   20x 2 + 21x + 4 < 0

•   ( 5x + 4 ) ( 4x + 1 ) < 0

•   20x 2 + 21x + 4 = 0  at  x = - 4 5  and  x = - 1 4
+0-0+

||||
|- 4 5 - 1 4 |
   We have to find values of x where 20x 2 + 21x + 4 < 0.


∴    - 4 5  <  x  <  - 1 4

For more info please see

Quadratic Equations