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#1 2017-01-14 22:08:44
- Primenumbers
- Member
- Registered: 2013-01-22
- Posts: 149
An easy way to find out if a number is prime.
p=Any number
A=2x3x5x7x11x13x17........ up to
m=Any multiple
A-pm= A number factorable by a factor of p
if p has one.To get A-pm, go through the primes, subtracting p as many times as you like.
Example:
p=129
A=2x3x5x7x11
2x3x5x7=210 210-129=81
81x11=891 891-(129x6)=117
A-129m=117
117 will have a factor the same as p if it has any.
117/129=39/43 129 is NOT prime (Common denominator =3)
In this way we can find out if p is composite without ever having to use a number
. Might be useful for computers."Time not important. Only life important." - The Fifth Element 1997
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