bonsoir
a. 5a(3 - 6a) - 4a = 15 a - 30 a² - 4 a = - 30 a² + 11 a
b. (3a - 2)(5 - 4a) - 3(7a - 2)
= 15 a - 12 a²- 10 + 8 a - 21 a + 6
= - 12 a² + 2 a - 4
c. 5a² - 4(3 - 7a) = 5 a² - 12 + 28 a
d.5(4a - 1) - (2a + 3)(-5a - 7)
= 20 a - 5 - ( - 10 a² - 14 a - 15 a - 21)
= 20 a - 5 + 10 a² + 14 a + 15 a + 21
= 10 a² + 49 a + 16
Exercice 2 : Factoriser les expressions suivantes
a. (2a + 3)(5a - 1) - (2a + 3)(4a - 7)
= ( 2 a + 3 ) ( 5 a - 1 - 4 a + 7)
= ( 2 a + 3 ) ( a + 6 )
b. (3a - 5)² - 3(2a + 7)(3a - 5)
= ( 3 a - 5 ) ( 3 a - 5 - 6 a - 21 )
= ( 3 a - 5 ) ( - 3 a - 26 )
c. (2a - 4)(-3a + 7) - 5(2a - 4) + (2a -4)(4a + 3)
= ( 2 a - 4 ) ( - 3 a + 7 - 5 + 4 a + 3 )
= ( 2 a - 4 ) ( a + 5 )
