Bonsoir
a. Volume parallélépipède = L × l × h
V1 (x) = AB × AC × BF = 9 × x
V1 (x) = 9x
Volume pyramide = 1/3 aire de la base × hauteur
V2 (x) = 1/3 × EF² × SM = 1/3 × 9 × (7-x)
V2 (x) = 3 (7-x)
V2 (x) = 21 - 3x
c. On veut V1 (x) = V2 (x)
9x = 21 - 3x
12x = 21
x = 21/12 = 1,75
d. On veut V1 (x) = 2 V2 (x)
9x = 2 ( 21 - 3x )
9x = 42 - 6x
15x = 42
x = 42/15 = 2,8
