Bonjour,
Aire du jardin rectangulaire = 2/3 aire du jardin triangulaire
Ar = 4x * ?
At = (3x - 3xy)(8x + 2y) / 2
Ar = 2/3 At
Ar = 2/3 (3x - 3xy)(8x + 2y) / 2
Ar = 2x(1 - y)(4x + y)
4x * ? = 2x(1 - y)(4x + y)
4x/2x * ? = (1 - y)(4x + y)
2 * ? = (1 - y)(4x + y)
? = 1/2 (1 - y)(4x + y)
Pr = 2 (4x + 1/2(1 - y)(4x + y))
Pr = 8x + (1 - y)(4x + y)
Pr = 8x + 4x + y - 4xy - y^2
Pr = 12x - y^2 - 4xy + y
Pr = 12x - y(y + 4x - 1)