bjr
y = -x + 1 et y = (1/3)x - 1
-x + 1 = (1/3)x - 1
-x - (1/3)x = -1 - 1
pour faciliter les calculs on multiplie les deux membres par -1
x + (1/3)x = 2
(3/3)x + (1/3)x = 2 [1er membre (3/3 + (1/3) x ]
(4/3)x = 2
x = 2 / (4/3)
x = 2 x (3/4)
x = 3/2
y = -x + 1
y = -3/2 + 1
y = -1/2
si on garde les signes - on obtient
-x - (1/3)x = -1 - 1
-(3/3)x - (1/3)x = -2
(-4/3)x = -2
etc.
