Question

[Vampire Princess]

Tìm các số nguyên tố x, y sao cho: x² + 117 = y²

Answer 1

[dao minh hieu]

(x-3).(y+2)=-5

⇒⇒(x-3).(y+2)=-1.5=-5.1

do x;y∈∈Z nen ta co bang sau:

x-3	-1	-5
y+2	5	1
x	2	-2
y	3	-1

vay:(x;y)∈∈{(2;3);(-2;-1)}