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Impossible Maths Number Riddle

Impossible Maths Number Riddle - 20 February

We know that the number 7 is the prime followed by a cube. Which next number is also a prime followed by a cube ?

* Its a popular maths trivia riddle.

Impossible Maths Number Riddle

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5 comments:

  1. x^3 - 1 = (x - 1)(x^2 + x + 1)

    This suggests that x^3 - 1 cannot be prime when x - 1 > 1, or x > 2, since x - 1 is a factor of x^3 - 1.

    When x = 2, we have the example given (7 and 8). All larger cubes cannot be preceded by a prime since x > 2 in those cases.

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  2. since for being prime no one of the right side equation should be 1.
    [x^3-1=(x-1)(x^2+x+1)]
    i.e. x-1=1 or x^2+x+1=1
    which gives x=-1,0,2
    in this -1,0 the cube comes to be the same as -1 and 0, which does not have the preceeding no -2,-1 which is not prime, so only one answer can be possible that is 2.
    2^3=8
    8-1=7

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  3. This comment has been removed by the author.

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  4. but 63 exists right, which is followed by 64,a cube..............!!!!

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