a: \(\Leftrightarrow\left(x+y;y-5\right)\in\left\{\left(1;16\right);\left(2;8\right);\left(4;4\right);\left(8;2\right);\left(16;1\right);\left(-4;-4\right);\left(-8;-2\right);\left(-16;-1\right)\right\}\)
\(\Leftrightarrow\left(x+y;y\right)\in\left\{\left(1;21\right);\left(2;13\right);\left(4;9\right);\left(8;7\right);\left(16;6\right);\left(-4;1\right);\left(-8;3\right);\left(-16;4\right)\right\}\)
\(\Leftrightarrow\left(x,y\right)\in\left\{\left(1;7\right);\left(10;6\right)\right\}\)
b: \(\Leftrightarrow\left(2x+3\right)\left(2y-1\right)=10\)
\(\Leftrightarrow\left(2x+3;2y-1\right)\in\left\{\left(1;10\right);\left(10;1\right);\left(2;5\right);\left(5;2\right);\left(-1;-10\right);\left(-10;-1\right);\left(-2;-5\right);\left(-5;-2\right)\right\}\)
mà 2x+3;2y-1 đều là các số lẻ
nên \(\left(x,y\right)\in\varnothing\)