Réponses

2013-10-06T10:53:03+02:00
1/ A=(a+1)(a+1)-(a-1)(a-1)
A= (a²+a+a+1)-(a²-a-a+1)
A=(a²+2a+1)-(a²-2a+1)
A=a²+2a+1-a²+2a-1
A=4a

2/

100001*100001-99999*99999 = (100000+1)*(100000+1)-(100000-1)*(100000-1)
a=100000 donc A=4*100000=400000