Question

tìm tất cả các cặp số nguyên x

a) (x+5) (y-2) = 7

b) (x-1) (xy + 2 ) =5

Answer 1

a: (x+5)(y-2)=7

\(\Leftrightarrow\left(x+5;y-2\right)\in\left\{\left(1;7\right);\left(7;1\right);\left(-1;-7\right);\left(-7;-1\right)\right\}\)

hay \(\left(x,y\right)\in\left\{\left(-4;9\right);\left(2;3\right);\left(-6;-5\right);\left(-12;1\right)\right\}\)

c: \(\left(x-1\right)\left(xy+2\right)=5\)

\(\Leftrightarrow\left(x-1;xy+2\right)\in\left\{\left(1;5\right);\left(5;1\right);\left(-1;-5\right);\left(-5;-1\right)\right\}\)

\(\Leftrightarrow\left(x,xy\right)\in\left\{\left(2;3\right);\left(6;1\right);\left(0;-7\right);\left(-4;-3\right)\right\}\)

hay \(\left(x,y\right)\in\left\{\left(2;\dfrac{3}{2}\right);\left(6;\dfrac{1}{6}\right);\left(-4;\dfrac{3}{4}\right)\right\}\)