Algebra


  1. The expression x4 – 2x² + k will be a perfect square when the value of k is









  1. View Hint View Answer Discuss in Forum

    (a – b)² = a² –2ab + b²
    x4– 2x² +k = (x²)² – 2.x2.1+ k
    ∴ k = (1)² = 1

    Correct Option: B

    (a – b)² = a² –2ab + b²
    x4– 2x² +k = (x²)² – 2.x2.1+ k
    ∴ k = (1)² = 1


  1. If x = ³√ a + √a² + b³ + ³√a - √a² + b³ , then x³ + 3bx is equal to









  1. View Hint View Answer Discuss in Forum

    x = ³√ a + √a² + b³ + ³√a - √a² + b³
    Cubing both sides,
    x³ = (³√ a + √a² + b³)³ + (³√a - √a² + b³)³ + (³√ a + √a² + b³)
    (³√a - √a² + b³)(³√ a + √a² + b³ + ³√a - √a² + b³)
    = a + √a² + b³ + a - √a² + b³ + 3 (a + √a² + b³ × a - √a² + b³)¹/3x
    = 2a + 3(a² - a² - b³)¹/3x
    = 2a + ( - 3bx)
    ∴ x³ + 3bx = 2a

    Correct Option: C

    x = ³√ a + √a² + b³ + ³√a - √a² + b³
    Cubing both sides,
    x³ = (³√ a + √a² + b³)³ + (³√a - √a² + b³)³ + (³√ a + √a² + b³)
    (³√a - √a² + b³)(³√ a + √a² + b³ + ³√a - √a² + b³)
    = a + √a² + b³ + a - √a² + b³ + 3 (a + √a² + b³ × a - √a² + b³)¹/3x
    = 2a + 3(a² - a² - b³)¹/3x
    = 2a + ( - 3bx)
    ∴ x³ + 3bx = 2a



  1. 1
    .
    1
    .
    1
    +
    1
    .
    1
    .
    1
    - 3 .
    1
    .
    1
    .
    1
    +
    1
    .
    1
    .
    1
    333444345555
    1
    .
    1
    +
    1
    .
    1
    +
    1
    .
    1
    -
    1
    .
    1
    +
    1
    .
    1
    +
    1
    .
    1
    334455344553

    is equal to :









  1. View Hint View Answer Discuss in Forum

    Let
    1
    = a,
    1
    = b, and
    1
    = c
    345

    ∴ Expression
    =
    a³ + b³ + c³ - 3abc
    a² + b² + c² - ab - ac - bc

    =
    (a + b + c) (a² + b² + c² - ab - ac - bc)
    = a + b + c
    a² + b² + c² - ab - ac - bc

    1
    +
    1
    +
    1
    =
    20 + 15 + 12
    =
    47
    3456060

    Correct Option: C

    Let
    1
    = a,
    1
    = b, and
    1
    = c
    345

    ∴ Expression
    =
    a³ + b³ + c³ - 3abc
    a² + b² + c² - ab - ac - bc

    =
    (a + b + c) (a² + b² + c² - ab - ac - bc)
    = a + b + c
    a² + b² + c² - ab - ac - bc

    1
    +
    1
    +
    1
    =
    20 + 15 + 12
    =
    47
    3456060


  1. When xm is multiplied by xn, product is 1. The relation between m and n is









  1. View Hint View Answer Discuss in Forum

    xm × xm = 1
    ⇒ xm+n = x0
    ⇒ m + n = 0
    ⇒ m = –n

    Correct Option: D

    xm × xm = 1
    ⇒ xm+n = x0
    ⇒ m + n = 0
    ⇒ m = –n



  1. The term, that should be added to (4x² + 8x) so that resulting expression be a perfect square, is









  1. View Hint View Answer Discuss in Forum

    (a + b)² = a² + 2ab + b²
    ∴ 4x² + 8x + 4
    = (2x)² + 2 × 2x × 2 + (2)²
    = (2x + 2)²
    ∴ Required number = 4

    Correct Option: B

    (a + b)² = a² + 2ab + b²
    ∴ 4x² + 8x + 4
    = (2x)² + 2 × 2x × 2 + (2)²
    = (2x + 2)²
    ∴ Required number = 4