Algebra


  1. If   a2 + b2 = 2 and c2 + d2 = 1, then the value of (ad – bc)2 + (ac + bd)2 is









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    (ad – bc)2 + (ac + bd)2
    = a2d2 + b2c2 – 2abcd + a2c2 +
    b2d2 + 2abcd
    = a2d2 + b2c2 + a2c2 +
    b2d2
    = a2d2 + b2d2 + b2c2 + a2c2
    = d2(a2 + b2) + c2(b2 + a2)
    = (a2 + b2) (c2 + d2)
    = 2 × 1 = 2

    Correct Option: D

    (ad – bc)2 + (ac + bd)2
    = a2d2 + b2c2 – 2abcd + a2c2 +
    b2d2 + 2abcd
    = a2d2 + b2c2 + a2c2 +
    b2d2
    = a2d2 + b2d2 + b2c2 + a2c2
    = d2(a2 + b2) + c2(b2 + a2)
    = (a2 + b2) (c2 + d2)
    = 2 × 1 = 2


  1. If   x2 = y + z, y2 = z + x, z2 = x + y,
    then the value of
    1
    +
    1
    +
    1
      is;
    x + 1x + 1z + 1









  1. View Hint View Answer Discuss in Forum

    Tricky Approach
    x2 = y + z
    ⇒  x2 + x = x + y + z
    ⇒  x (x + 1) = x + y + z ....(i)
    Similarly,
    y (y + 1) = x + y + z    .........(ii)
    and, z (z + 1) = x + y + z    ...(iii)

    ∴ 
    1
    +
    1
    +
    1
    x + 1x + 1z + 1

    =
    x
    +
    y
    +
    z
    x + y + zx + y + zz + y + z

    ⇒ 
    x + y + z
    = 1
    x + y + z

    Correct Option: B

    Tricky Approach
    x2 = y + z
    ⇒  x2 + x = x + y + z
    ⇒  x (x + 1) = x + y + z ....(i)
    Similarly,
    y (y + 1) = x + y + z    .........(ii)
    and, z (z + 1) = x + y + z    ...(iii)

    ∴ 
    1
    +
    1
    +
    1
    x + 1x + 1z + 1

    =
    x
    +
    y
    +
    z
    x + y + zx + y + zz + y + z

    ⇒ 
    x + y + z
    = 1
    x + y + z



  1. If   p + q = 10 and pq = 5, then the numerical value of
    p
    +
    q
    will be
    qp









  1. View Hint View Answer Discuss in Forum

    p
    +
    q
    =
    p² + q²
    pqpq

    =
    (p + q) - 2pq
    pq

    =
    100 - 2 × 5
    =
    90
    = 18
    55

    Correct Option: D

    p
    +
    q
    =
    p² + q²
    pqpq

    =
    (p + q) - 2pq
    pq

    =
    100 - 2 × 5
    =
    90
    = 18
    55


  1. If a1/3 =11, then the value of a2 – 331a is









  1. View Hint View Answer Discuss in Forum

    a1/3 =11 ⇒ a = 113 = 1331
    ∴  a2 – 331a = a(a – 331)
    = 1331 (1331 – 331)
    = 1331 × 1000 = 1331000

    Correct Option: B

    a1/3 =11 ⇒ a = 113 = 1331
    ∴  a2 – 331a = a(a – 331)
    = 1331 (1331 – 331)
    = 1331 × 1000 = 1331000



  1. If 1.5x = 0.04y, then the value of  
    y2 − x2
    is
    y2 + 2xy + x2









  1. View Hint View Answer Discuss in Forum

    1.5x = 0.04y

    ⇒ 
    x
    =
    0.04
    =
    4
    =
    2
    y1.515075

    ⇒ 
    y
    =
    75
    x2

    Now,  
    y2 − x2
    y2 + 2xy + x2

    =
    (y − x)(y + x)
    (y + x)2

    =
    y − x
    y + x

    =
    y
    − 1
    x
    y
    + 1
    x

    =
    75
    − 1
    2
    75
    + 1
    2

    =
    73
    77

    Correct Option: B

    1.5x = 0.04y

    ⇒ 
    x
    =
    0.04
    =
    4
    =
    2
    y1.515075

    ⇒ 
    y
    =
    75
    x2

    Now,  
    y2 − x2
    y2 + 2xy + x2

    =
    (y − x)(y + x)
    (y + x)2

    =
    y − x
    y + x

    =
    y
    − 1
    x
    y
    + 1
    x

    =
    75
    − 1
    2
    75
    + 1
    2

    =
    73
    77