Ex. 2 :
a) et b) P=5x+2(x+3)+7x+1+10x-0,5 = 24x+6,5
c) si x=5, P = 24(5)+6,5 = 126,5
Ex. 3 :
a) aire totale = 4x(x+5) + 2x(x-3) = 4x²+20x+2x²-6x = 6x²+14x
b) et c) V = x(x-3)(x+5) = x(x²+5x-3x-15) = x³+2x²-15x
d) si x=15 cm
V=15³+2(15²)+15(15)= 4 050 cm³ = 4,05 dm³ = 4,05 Litres
si x=20
V=20³+2(20²)+15(20)= 9 100 cm³ = 9,1 dm³ = 9,1 Litres
