Exercice 1:

Il faut multipier les quantites de chaque ingredient par 2 ---  ( 2 litres / 1 litres)

Exercice 2:

A = -6 x^2 + 4 x^2 + 1 = - 2 x^2 + 1

B = 5x + x^2 + 4x = x^2 + 9 x

C = 7x + 5 + x – 9 = 8 x -4

D = 10 – x – 4x  -6 = - 5 x + 4

Exercice 3:

AC^2 = AB^2 – BC^2 = 9^2 – 7,2^2 = 29.16

AC = 5,4 cm

JC = AC/2 = 2,7cm

IC = BC/2 = 3,6 cm

BJC  est un triangle rectangle en C.

BJ^2 = BC^2 + JC^2 = 7,2^2 + 2,7^2 = 59.13

BJ = 7,6896 cm   = 76.896 mm

AIC est un triangle rectangle en C.

AI^2 = AC^2 + IC^2 = 5,4^2 + 3,6^2 = 42.12

AI = 6.48999 cm   =  64.8999 mm

Exercice 4 :

Nature de la base  --    rectangle , triangle ,  pentagone

Nature des faces laterales -  triangle , triangle , triangle

Exercice 5 :

 36 minutes --     car    18 minute s * 6 chainettes / 3 chainettes = 36