Question

方程p+q+r+pq+rq+rp=pqr+1所有正整数解p≤q≤r

Answer 1

假设 p≥4 ,则 r≥q≥p≥4 ,4r>3r≥r+q+p,rq≥rp≥qp,3qr≥pq+rq+rp,p+q+r+pq+rq+rp≤3r+3q