Re: [math-fun] Reminder needed: For what rational a is -8 + 36 a - 27 a^2 square?

I didn't follow math-fun for a long time (i.e., don't know where this equation came from), but the new subject caught my eye. Using an elementary method, I found that -8 + 36*a - 27*a^2 is a rational square iff a = 2/3 + (4/3)*k/(k^2+3) for some rational k. On Sat, Aug 1, 2015 at 11:53 PM, Bill Gosper <billgosper@gmail.com> wrote:

The data are intriguing. Something about 3 and powers of primes 1 mod 6. What subject is this? BQFs? --rwg _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun