**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.

**For Solution :**Click Here

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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.

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

ReplyDeleteThis 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.

since for being prime no one of the right side equation should be 1.

ReplyDelete[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

This comment has been removed by the author.

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

ReplyDelete63/9=7

Delete