Bonjour,
Vérifier par calcul.
{ x-y= -1
{-x+7y= -17
-----------------
6y= -18, y= -18/6, y= -3
x= -1+y , x= -1-3; x= -4
S= {( -4; -3 )}
{-5 x-y= -13
{x-y= -1 ⇒ x= -1+y; -5(-1+y)-y= -13; 5-5y-y= -13; -6y= -13-5; y= -18/-6
y= 3
x= -1+3
x= 2
S= {( 2: 3 )}
{ -x+7y= -17 ⇒ x= 17+7y
{-5x-y= -13
-5(17+7y)-y= -13; -85-35y-y= -13; -36y= -13+85; y= -72/36; y= -2
x= 17+7(-2) ; x= 17-14; x= 3
S= {( 3; -2 )}
