Quadratic Equation


Direction: In each of these questions, two equations are given. You have to solve these equations and find out the values of x and y and Give answer
( 1 ) if x < y
( 2 ) if x > y
( 3 ) if x ≤ y
( 4 ) if x ≥ y
( 5 ) if x = y

  1. Ⅰ. 16x2 + 20x + 6 = 0
    Ⅱ.10y2 + 38y + 24 = 0











  1. View Hint View Answer Discuss in Forum

    As per the given above equations , we can say that
    Ⅰ.
    16x2 + 20x + 6 = 0
    ⇒ 16x2 + 12x + 8x + 6 = 0

    Ⅱ.
    10y2 + 38y + 24 = 0
    ⇒ 10y2 + 30y + 8y + 24 = 0
    ⇒ 10y(y + 3) + 8(y + 3) = 0

    Correct Option: B

    As per the given above equations , we can say that
    Ⅰ. 16x2 + 20x + 6 = 0
    ⇒ 16x2 + 12x + 8x + 6 = 0
    ⇒ 4x(4x + 3) + 2(4x + 3) = 0
    ⇒ (4x + 2)(4x + 3) = 0

    ⇒ x = -
    3
    , -
    2
    4
    4
    Ⅱ.10y2 + 38y + 24 = 0
    ⇒ 10y2 + 30y + 8y + 24 = 0
    ⇒ 10y(y + 3) + 8(y + 3) = 0
    ⇒ (10y + 8)(y + 3) = 0
    ⇒ y = - 3, -
    4
    5
    ∴ x > y
    From above both equations it is clear that correct answer is x > y .


  1. Ⅰ. 17x2 + 48x = 9
    Ⅱ.13y2 = 32y –12











  1. View Hint View Answer Discuss in Forum

    From the given above equations , we have
    From equation Ⅰ.
    17x2 + 48x − 9 = 0
    ⇒ 17x2 + 51x − 3x − 9 = 0

    From equation Ⅱ.
    13y2 − 32y + 12 = 0
    ⇒ 13y2 − 26y − 6y + 12 = 0

    Correct Option: A

    From the given above equations , we have
    From equation Ⅰ.
    17x2 + 48x − 9 = 0
    ⇒ 17x2 + 51x − 3x − 9 = 0
    ⇒ 17x(x + 3) − 3(x + 3) = 0
    ⇒ (17x − 3)(x + 3) = 0

    ⇒ x = - 3,
    3
    17

    From equation Ⅱ.
    13y2 − 32y + 12 = 0
    ⇒ 13y2 − 26y − 6y + 12 = 0
    ⇒ 13y(y − 2) − 6(y − 2) = 0
    ⇒ (13y − 6)(y − 2) = 0
    ⇒ y = 2,
    6
    13



  1. The roots of the equation a2x2 - 3abx + 2b2 = 0 are









  1. View Hint View Answer Discuss in Forum

    The given quadratic equation is
    a2x2 - 3abx + 2b2 = 0 &⇒ a 2 x 2 - 3abx + 2b 2 = 0
    ⇒ ax ( ax - 2b ) - b ( ax - 2b ) = 0
    ⇒ ( ax - 2b ) ( ax - b ) = 0
    ⇒ ax - 2b = 0 or ax - b = 0

    ⇒ x =
    2b
    or x =
    b
    a
    a

    Correct Option: B

    The given quadratic equation is
    a 2 x 2 - 3abx + 2b 2 = 0 &⇒ a 2 x 2 - 3abx + 2b 2 = 0
    ⇒ ax ( ax - 2b ) - b ( ax - 2b ) = 0
    ⇒ ( ax - 2b ) ( ax - b ) = 0
    ⇒ ax - 2b = 0 or ax - b = 0

    ⇒ x =
    2b
    or x =
    b
    a
    a

    Thus, the two roots of the given quadratic equation are
    2b
    and
    b
    a
    a


  1. If α and β are the roots of the quadratic equation ax 2 + bx + c = 0, the value of α3 + β3 is









  1. View Hint View Answer Discuss in Forum

    According to question , we can say that
    Since α and β are the roots of the quadratic equation
    ax 2 + bx + c = 0

    ∴ α + β = −
    b
    and αβ =
    c
    a
    a

    Correct Option: B

    According to question , we can say that
    Since α, β are the roots of the quadratic equation
    ax 2 + bx + c = 0

    ∴ α + β = −
    b
    and αβ =
    c
    a
    a

    Now, α 3 + β 3 = ( α + β ) 3 - 3αβ( α + β )
    =-
    b
    3- 3 x
    c
    x
    - b
    aaa
    α3 + β3 =
    - b 3
    +
    3bc
    =
    - b2 + 3abc
    a3a2a3

    Hence , α3 + β3 =
    b ( 3ac - b2 )
    a 3



  1. For what value of k the quadratic polynomial 3z2 + 5z + k can be factored into product of real linear factors ?









  1. View Hint View Answer Discuss in Forum

    We have , the given quadratic eq. 3z 2 + 5z + k
    Comparing it with ax 2 + bx + c = 0, we get a = 3, b = 5, c = k
    Now , D = b2 - 4ac = 25 - 12k
    For equal linear factors to exist, D ≥ 0
    ⇒ 25 - 12k ≥ 0
    ⇒ 25 ≥ 12k

    Correct Option: B

    We have , the given quadratic eq. 3z 2 + 5z + k
    Comparing it with ax 2 + bx + c = 0, we get a = 3, b = 5, c = k
    Now , D = b2 - 4ac = 25 - 12k
    For equal linear factors to exist, D ≥ 0
    ⇒ 25 - 12k ≥ 0
    ⇒ 25 ≥ 12k

    ⇒ k ≤
    25
    12
    Therefore, the set of real numbers ≤
    25
    gives the set of value of k for which the given
    12
    quadratic polynomial can be factored into the product of real linear factors.