Question

Решить систему уравнений х^2-у^2=-4,х^2+у^2=12

Answer 1

$( {x}^{2} - {y}^{2} ) + ( {x}^{2} + {y}^{2} ) = - 4 + 12$
$2 {x}^{2} = 8$
${x}^{2} = 4$
$x = - 2$
$x = 2$
$4 + {y}^{2} = 12$
${y}^{2} = 8$
$y = \sqrt{8}$
$y = - \sqrt{8}$