Simplification


  1. If x + 1/x = 6, then x4 + 1/x4 is ?









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    x + 1/x = 6
    On squaring both sides, we get
    (x + 1/x)2 = (6)2
    ⇒ x2 + 1/x2 + 2 = 36
    ⇒ x2 + 1/x2 = 34

    Correct Option: B

    x + 1/x = 6
    On squaring both sides, we get
    (x + 1/x)2 = (6)2
    ⇒ x2 + 1/x2 + 2 = 36
    ⇒ x2 + 1/x2 = 34
    On squaring both sides, we get
    (x2 + 1/x2)2 = (34)2
    ⇒ x4 + 1/x4 + 2 = 1156
    ⇒ x4 + 1/x4 = 1154


  1. If x + 1/x = 2, then what is value of x - 1/x ?









  1. View Hint View Answer Discuss in Forum

    Given that, x + 1/x = 2 ...........................(i)
    On squaring both sides, we get
    (x + 1/x)2 = 4
    ⇒ x2 + 1/x2 + 2 = 4
    ⇒ x2 + 1/x2 = 2 ...............................(ii)
    Now, we have
    (x - 1/x)2 = (x2 + 1/x2) - 2x X 1/x

    Correct Option: A

    Given that, x + 1/x = 2 ...................(i)
    On squaring both sides, we get
    (x + 1/x)2 = 4
    ⇒ x2 + 1/x2 + 2 = 4
    ⇒ x2 + 1/x2 = 2 ..................................(ii)
    Now, we have
    (x - 1/x)2 = (x2 + 1/x2) - 2x X 1/x
    now put the value of x2 + 1/x2
    (x - 1/x)2 = 2 - 2 = 0 [from Eq. (ii)]
    ∴ x - 1/x = 0



  1. If x + 1/x = 3, then x5 + 1/x5 is equal to ?









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    x + 1/x = 3 ................. (i)
    On squaring both side, we will get
    (x + 1/x)2 = (3)2

    Correct Option: A

    x + 1/x = 3 ........................ (i)
    On squaring both side, we will get
    (x + 1/x)2 = (3)2
    Use the Square algebra formula (a + b)2 = a2 + 2ab + b2
    ⇒ x2 + 1/x2 + 2 = 9
    ⇒ x2 + 1/x2 = 7 ..................(ii)
    Again squaring both sides, we will get
    (x2 + 1/x2)2 = (7)2
    Use the Square algebra formula (a + b)2 = a2 + 2ab + b2
    ⇒ x4 + 1/4 + 2 = 49
    ⇒ x4 + 1/x4 = 47 .....................(iii)
    On cubing the equation (i) both side, we will get
    (x + 1/x)3 = (3)3
    Use the cube algebra formula (a + b)3 = a3 + 3a2b + 3ab2 + b3
    ⇒ x3+ 1/x3 + 3(x + 1/x) = 27
    ⇒ x3 + 1/x3 + 9 = 27 [∴ (x + 1/x) = 3]
    ⇒ x3 + 1/x3 = 18 ...................(iv)
    On multiplying Eqs. (i) and (iii) , we get
    ∴ (x4 + 1/x4) (x + 1/x) = 47 x 3
    ⇒ x5 + 1/x5 + x3 + 1/x3 = 141
    ⇒ x5 + 1/x5 + 18 = 141 [from Eq. (iv)]
    ⇒ x5 + 1/x5 = 123


  1. 3x + 2y = 12 and xy = 6, them the value of 9x2 + 4y2 is ?









  1. View Hint View Answer Discuss in Forum

    Given equation are
    3x + 2x = 12 ...................(i)
    xy = 6 ..............................(ii)
    On squaring Eq. (i) on both sides and put the value of xy and solve the equation.

    Correct Option: C

    Given equation are
    3x + 2y = 12 ..............(i)
    xy = 6 .........................(ii)
    On squaring Eq. (i) on both sides, we will get
    (3x + 2y)2 = (12)2
    ⇒ 9x2 + 4y2 + 12xy = 144
    put the value of xy
    ⇒ 9x2+ 4x2 = 144 - 72 = 72
    ⇒ 9x2+ 4x2 = 72



  1. (4 x 4 x 4 x 4 x 4 x 4)5 x (4 x 4 x 4 )8 ÷ (4)3 = (64)?









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    (4 x 4 x 4 x 4 x 4 x 4)5 x (4 x 4 x 4)8 ÷ (4)3 = (64)?`
    Apply the law of Fractional Exponents and Laws of Exponents
    if a multiply n times a x a x a x....up to n times, then
    a x a x a x a ......up to n times = an

    ⇒ (46)5 x (43)8 x 1/(4)3 = (43)?

    Correct Option: A

    (4 x 4 x 4 x 4 x 4 x 4)5 x (4 x 4 x 4)8 ÷ (4)3 = (64)?
    Apply the law of Fractional Exponents and Laws of Exponents
    if a multiply n times a x a x a x....up to n times, then
    a x a x a x a ......up to n times = an
    By simplifying the equation
    ⇒ (46)5 x (43)8 x 1/(4)3 = (43)?
    ⇒ (4)30 x (4)24/(4)3 = (4)3 x ?
    ⇒ 430 + 24 - 3 = 43 x 7
    And comparing the exponents both the sides
    ⇒ 451 = 43 x ? ⇒ 3 x ? = 51
    ∴ ? = 51/3 = 17