Question

Tìm x,y\(\in\)N sao cho xy-5x+y=17

Answer 1

\(xy-5x+y=17\)

\(\Rightarrow x\left(5-y\right)+y=17\)

\(\Rightarrow x\left(5-y\right)-5+y=17-5\)

\(\Rightarrow x\left(5-y\right)-\left(5-y\right)=12\)

\(\Rightarrow\left(x-1\right)\left(5-y\right)=12\)

\(\Rightarrow\left(x-1\right);\left(5-y\right)\inƯ\left(12\right)=\left\{\pm1;\pm2;\pm3;\pm4;\pm6;\pm12\right\}\)

Xét bảng 

x-1	1	-1	2	-2	3	-3	4	-4	6	-6	12	-12
5-y	12	-12	6	-6	4	-4	3	-3	2	-2	1	-1
x	2	0	3	-1	4	-2	5	-3	7	-5	13	-11
y	-7	17	-1	11	1	9	2	8	3	7	4	6

Vậy.....................................

P/s : ko chắc