Question

[Trần Hà Ngân]

tìm x,y thuộc Z

a) (x-1).(y+1)=-5

b)(x-3).(2y+1)=7

c) (2x+1).(3y-2)=-55

Answer 1

[Nguyễn Lê Phước Thịnh]

a: (x-1)(y+1)=5

nên \(\left(x-1;y+1\right)\in\left\{\left(1;5\right);\left(5;1\right);\left(-1;-5\right);\left(-5;-1\right)\right\}\)

hay \(\left(x,y\right)\in\left\{\left(2;4\right);\left(6;0\right);\left(0;-6\right);\left(-4;-2\right)\right\}\)

b: (x-3)(2y+1)=7

\(\Leftrightarrow\left(x-3;2y+1\right)\in\left\{\left(1;7\right);\left(7;1\right);\left(-1;-7\right);\left(-7;-1\right)\right\}\)

hay \(\left(x,y\right)\in\left\{\left(4;3\right);\left(10;0\right);\left(2;-4\right);\left(-4;-1\right)\right\}\)