Question

Tìm tất cả các cặp số nguyên thỏa mãn y(x-1)=\(^{x^2}\)+2

Answer 1

Ta có:\(y\left(x-1\right)=x^2+2\)

\(\Rightarrow y\left(x-1\right)-x^2=2\)

\(\Rightarrow y\left(x-1\right)-x^2+1=3\)

\(\Rightarrow y\left(x-1\right)-\left(x^2-1\right)=3\)

\(\Rightarrow y\left(x-1\right)-\left(x+1\right)\left(x-1\right)=3\)

\(\Rightarrow\left(y-x-1\right)\left(x-1\right)=3\)

Vì x,y nguyên nên ta có bảng

x-1	3	1	-1	-3
y-x-1	1	3	-3	-1
x	4	2	0	-2
y	6	8	2	4

Vậy \(\left(x,y\right)\in\left\{\left(4,6\right);\left(2,8\right);\left(0,2\right);\left(-2,4\right)\right\}\) thỏa mãn