Question

x+xy+y=9

cần lời giải thích

Answer 1

=>x(y+1)+y+1=10

=>(x+1)(y+1)=10

=>\(\left(x+1;y+1\right)\in\left\{\left(1;10\right);\left(10;1\right);\left(-1;-10\right);\left(-10;-1\right);\left(2;5\right);\left(5;2\right);\left(-5;-2\right);\left(-2;-5\right)\right\}\)

=>\(\left(x,y\right)\in\left\{\left(0;9\right);\left(9;0\right);\left(-2;-11\right);\left(-11;-2\right);\left(1;4\right);\left(4;1\right);\left(-3;-6\right);\left(-6;-3\right)\right\}\)