Verified answer

II a)  E = (2a + 1)(3a - 5) - (3a - 5)²

        = 6a² - 10a + 3a ²- 5 - 9a² + 30a - 25

        = - 3a² + 23a - 30

b) E = (2a + 1)(3a - 5) - (3a - 5)²

       = (3a - 5)(2a + 1 - 3a + 5)

       = (3a - 5)(6 - a)

c) f(6) = - 3(6)² + 23 (6) - 30

          = 30 - 30 = 0

f(6) = 0

d) f(x) = 0 ⇒ x = 6 ; x = 5/3

sin11.5° = 3.24/AB⇒ AB = 3.24/sin11.5° = 16.28 cm

v = AB/t  = 16.28/ 27 = 0.6 m/s 

0.6 x 10-³/1/3600 = 2.16 km/h

Pyramide

a) BD = 2√5 = 71 mm

b√) tan64° = OS/OB ⇒ OS = OBxtan64° = 73 mm

c) vous le faite vous même