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Old 2020-03-22, 15:30   #4
xilman's Avatar
May 2003
Down not across

2·3·1,699 Posts

Originally Posted by LaurV View Post
Neee.. gotcha! (so long I waited for that! )
r must be prime, I guess you didn't know that 1 is not considered a prime
Fairy Nuff: I over-looked that condition.

OK, choose r=2. Prime, right?

Let b=17, so B^2-100r = 289-200 = 89 = a. All are positive and co-prime.

Let b=19, so b^2-100r = 361-200 = 161 = 7 * 23 = a. All are positive and co-prime.

Let b=21, so a=241 which is a prime.

And so on.

It is still a trivial problem.
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