Quadratic Equation


Direction: In the following questions two equations numbered I and II are given. You have to solve both the equations and give answer
( 1 ) if x > y
( 2 ) if x ≥ y
( 3 ) if x < y
( 4 ) if x ≤ y
( 5 ) if x = y or the relationship cannot be established.

  1. Ⅰ. 2x2 + 11x + 14 = 0
    Ⅱ. 4y2 + 12y + 9 = 0











  1. View Hint View Answer Discuss in Forum

    From the given equations , we have
    Ⅰ. 2x2 + 11x + 14 = 0
    ⇒ 2x2 + 7x + 4x + 14 = 0
    ⇒ x( 2x + 7 ) + 2( 2x + 7 ) = 0

    Ⅱ. 4y2 + 12y + 9 = 0
    ⇒ ( 2y + 3 )2 = 0

    Correct Option: C

    From the given equations , we have
    Ⅰ. 2x2 + 11x + 14 = 0
    ⇒ 2x2 + 7x + 4x + 14 = 0
    ⇒ x( 2x + 7 ) + 2( 2x + 7 ) = 0
    ⇒ ( x + 2 )( 2x + 7 ) = 0

    ⇒ x =
    -7
    or -2
    2

    Ⅱ. 4y2 + 12y + 9 = 0
    ⇒ ( 2y + 3 )2 = 0
    ⇒ ( 2y + 3 )( 2y + 3 ) = 0
    ⇒ y =
    -3
    ,
    -3
    2
    2
    From above both equations it is clear that x < y is correct answer .


  1. The roots of the equation ax2 + bx + c = 0 will be reciprocal if









  1. View Hint View Answer Discuss in Forum

    As we know that ,
    For reciprocal roots, product of roots must be 1

    c
    = I ⇒ c = a
    a

    Correct Option: C

    As we know that ,
    For reciprocal roots, product of roots must be 1

    c
    = I ⇒ c = a
    a

    Thus , required answer is c = a .



  1. Find the value of 30 + √30 + √30 +........









  1. View Hint View Answer Discuss in Forum

    According to question ,we can say that
    Let , x = √30 + √30 + √30 +........
    On squaring both sides, we have
    x2 = 30 + √30 + √30 + √30 +........
    ⇒ x2 = 30 + x ⇔ x2 - x - 30 = 0
    ⇒ x2 - 6x + 5x - 30 = 0

    Correct Option: C

    According to question ,we can say that
    Let , x = √30 + √30 + √30 +........
    On squaring both sides, we have
    x2 = 30 + √30 + √30 + √30 +........
    ⇒ x2 = 30 + x ⇔ x2 - x - 30 = 0
    ⇒ x2 - 6x + 5x - 30 = 0
    ⇒ x( x - 6 ) + 5( x - 6 ) = 0
    ⇒ ( x - 6 ) ( x + 5 ) = 0
    ⇒ x = 6 because x ≠ - 5
    Hence , required answer is 6 .


  1. The sum of the squares of 2 natural consecutive odd numbers is 394. The sum of the numbers is :









  1. View Hint View Answer Discuss in Forum

    Let, the two natural consecutive odd numbers be n and (n + 2)
    Now, according to the question,
    ⇒ n2 + ( n + 2 )2 = 394
    ⇒ n2 + n2 + 4 + 4n = 394

    Correct Option: D

    Let, the two natural consecutive odd numbers be n and (n + 2)
    Now, according to the question,
    ⇒ n2 + ( n + 2 )2 = 394
    ⇒ n2 + n2 + 4 + 4n = 394
    ⇒ 2n2 + 4n - 390= 0
    ⇒ n2 + 2n - 195 = 0
    ⇒ n2 + 15n - 13n - 195 = 0
    ⇒ n( n + 15 ) - 13( n + 15 ) = 0
    ⇒ ( n + 15 ) ( n - 13 ) = 0
    ⇒ n = 13 and n ≠ - 15
    ∴ The two natural consecutive odd numbers be 13 and (13 + 2) = 15 .
    ∴ the sum of the numbers = 13 + 15 = 28
    Quicker Approach:
    By mental operation, 132 + 152 = 169 + 225 = 394
    ∴ Required sum = 13 + 15 = 28



  1. One root of the equation 3x2 - 10x + 3 = 0 is
    1
    . Find the other root.
    3









  1. View Hint View Answer Discuss in Forum

    The given quadratic equation is 3x2 - 10x + 3 = 0
    Comparing with ax2 + bx + c = 0, we get
    a = 3, b = −10, c = 3

    Correct Option: A

    The given quadratic equation is 3x2 - 10x + 3 = 0
    Comparing with ax2 + bx + c = 0, we get
    a = 3, b = −10, c = 3

    ∴ Sum of the roots ( k1 + k2 ) = -
    a
    =
    10
    b
    3
    ∵ One root k1 =
    1
    3
    ∴ The other root k2 =
    10
    -
    1
    =
    9
    = 3.
    3
    3
    3

    Therefore , The other root is 3 .