Bonjour pouvez vous m'aider à résoudre ceci merci

xy = 27
(x+2)(y+1) = xy+17

xy = 27
xy+x+2y+2 = xy+17

xy = 27
xy-xy+x+2y = 17-2

xy = 27
x+2y = 15

x = -2y+15
(-2y+15)*y = 27
-2y²+15y-27 = 0

b²-4ac = 15²-4(-2*-27) = 9
Δ = 9

-b-√Δ/2a = -15-3/-4 = 18/4 = 9/2
-b+√Δ/2a = -15+3/-4 = 3

si x = L = 3cm
l = 9cm
A = 27
A augmenté = 11*4 = 44 soit 17cm² de plus