Question

Determinati multimea A={x,y | x^2+y^2=1, x,y apartin lui Z}

Answer 1

$\it x^2+y^2=1 \Leftrightarrow y^2 = 1-x^2 \Leftrightarrow \sqrt{y^2} =\sqrt{1-x^2 } \Leftrightarrow | y| = \sqrt{1-x^2} \\\;\\ \Leftrightarrow \it y = \pm \sqrt{\it 1-x^2} \ \ \ (*)$