va rog frumos am nevoie repede
dau coroana

Răspuns:
Explicație pas cu pas:
4. A= 2(1+2+3+...+2008)= 2· 2008·2009/2= 2008·2009
B= 2008·(1/2)·(2/3)·(3/4)·.......·(2008/2009)= 2008/2009
√(A-2009·B)= √(2008·2009-2009·(2008/2009)= √(2008·2009-2008)=
√2008(2009-1)= √2008²= 2008