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greenman
Lv 6
greenman asked in Science & MathematicsMathematics · 8 years ago

Is x! + 1 always a prime number If "no" give example.?

6 Answers

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  • ?
    Lv 4
    8 years ago
    Favorite Answer

    No equation exists that always produces a prime number, if you could manage to prove one somewhere would owe you a PhD

  • Jake
    8 years ago

    No, because,

    5!+1

    5 x 4 x 3 x 2 x 1 = 120

    120+1=121

    121/11=11

    Therefore it's not prime,

  • Mary75
    Lv 6
    8 years ago

    No. Here are two examples:

    5! + 1 = 121

    121 = 11 x 11

    6! + 1 = 721

    721 = 7 x 103

  • L. E. Gant
    Lv 7
    8 years ago

    Well, it will always be an odd number...

    4! + 1 = 25

    5! + 1 = 121

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  • grunfeld
    Lv 7
    8 years ago

    No and here is a counterexample.

    4! + 1

    = 24 + 1

    = 25 ( composite number because the factors of this are 1, 5 and 25 )

    Source(s): my brain
  • Star
    8 years ago

    Try x=4.

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