P be odd prime, m = 5p. Show that there is a primitive root mod m.
If [math]p>3[/math] is a prime, how can one show that if [math]p^k + p^l + p^m = n^2[/math] has natural solutions [math]k,l,m,n[/math], [math]p+1[/math] is divisible by [math]8[/math]?