Question

13n-9 supra 5n+7 apartine Z pentru care valori ale lui n

Answer 1

5n+7/13n-9 inmultim cu 5
5n+7/65n-45

5n+7/5n+7 inmultim cu 13
5n+7/65n+91

scadem  5n+7/136

5n+7∈{+1,.-1,+136,-136,+2,-2,+68,-68,+4,-4,+34,-34,+8,-8,+17,-17} /-7

5n∈{-6,.-8,+129,-143,-5,-9,+61,-75,-3,-11,+27,-41,+1,-15,+10,-24} /:5

n∈{-1,-15,-3,+2}