Réponse :

Bonjour

Explications étape par étape

Ex1)

1) Thalès

AB/AO = BC/OS

3.20/8 = 1/OS

OS*3.20=8*1

OS = 8/3.20

OS = 2.50m

2)Vcône=1/3*pi*r^2*h

V = 1/3*pi*(2.5)^2*2.5

V~16.36m^3

Ex2)

M = 2/5 - 4/3 + 7/2

M = 12/30 - 40/30 + 105/30

M = 77/30

N = (-7/4 + 1/2) : (2/7 + 1/4)

N = (-7/4 + 2/4) : (8/28 + 7/28)

N = -5/4 : 15/28

N = -5/4 * 28/15

N = (-5*7*4)/(4*5*3)

N = -7/3

L = (-28/5)/-21

L = (-28/5)* (-1/21)

L = (-7*4*(-1))/(5*7*3)

L = 4/15

2)

M(inverse) = 30/77

3)

N(opposé) = 7/3