Bonsoir !
Développer :
(4a-5)(4a-3)= 16a²-12a-20a+15 = 16a²-32a+15
(2a-5)(a-4) -5a = 2a²-8a-5a -20 = 2a²-13a-20a
17-(a+5)(a-3) = 17-(a²-3a+5a-15)= 17-a²+3a-5a+15 =-a²-2a+32
Factoriser :
32a - 8a² = 8a(4-a)
Bon courage
