Question

tìm x,y là số tự nhiên xy + x + y = 170

Answer 1

\(xy+x+y=170\left(n\inℕ\right)\)

\(\Rightarrow x\left(y+1\right)+y+1-1=170\)

\(\Rightarrow\left(x+1\right)\left(y+1\right)=171\)

\(\Rightarrow\left(x+1\right);\left(y+1\right)\in U\left(171\right)=\left\{1;3;9;19;57;171\right\}\)

\(\Rightarrow\left(x;y\right)\in\left\{\left(0;170\right);\left(2;56\right);\left(8;18\right);\left(18;8\right);\left(56;2\right);\left(170;0\right)\right\}\)