7.CMr: 
n nguyên dương và 2 dãyhttp://dientuvietnam.net/cgi-bin/mimetex.cgi?a_{i} vàhttp://dientuvietnam.net/cgi-bin/mimetex.cgi?b_{i} 1 
i 
n thỏa mãn :http://dientuvietnam.net/cgi-bin/mimetex.cgi?a_{i}+http://dientuvietnam.net/cgi-bin/mimetex.cgi?b_{i}
http://dientuvietnam...tex.cgi?a_{i 1} (mod p) 1 i n (coi http://dientuvietnam...tex.cgi?a_{n 1} )
