Réponses

2014-02-25T19:12:22+01:00
(x-4)(y+2,5)=60
xy = 60 
donc xy + 2,5x - 4y - 10 = 60 ou 60 
+ 2,5x - 4y - 10 = 60 => 2,5x - 4y = 10
2,5x - 4y = 10
                          => 2,5x - 240/x = 10 => 2,5x² - 10x - 240 = 0 
y = 60/x
2,5x² - 10x - 240 = 0  => x = 12 ou x = -8 
si x = 12 alors y = 60/12 = 5   => (12;5)
si x = -8 alors y = 60/-8 => y = -7,5 => (-8 ; -7,5)