Réponses

2013-02-05T19:31:31+01:00

a) P = (4a-5)(2a-3)+(5a+7)(4a-5)

P = 8a²-12a-10a+15+(20a²-25a+28a-35)

= 8a²-12a-10a+15+20a²-25a+28a-35

P = 28a²-19a-20

b) P = (4a-5)(2a-3)+(5a+7)(4a-5)

= (4a-5)[(2a-3)+(5a+7)}

=(4a-5)(2a-3+5a+7)

P = (4a-5)(7a+4)

 

c) a=0

P = (4*0-5)(7*0+4)= -5*4 = -20