Explicație pas cu pas:
b=2/4+2/6+2/8+....+2/4020 simplificam fractiile cu 2 si obtinem : b=1/2+1/6+1/4+....+1/2010
a+b= 1/2+2/3+3/4+.....+2009/2020+1/2+1/3+1/4+...+1/2010 grupam termenii cu acelasi numitor si obtinem :
a+b= (1/2+1/2) + (2/3+1/3) + (3/4+1/4) + ...... + (2009/2010+1/2010)= 2/2 + 3/3 + 4/4 + .... + 2010/2010= 1 + 1+1+....+1 ( 1 de 2010 ori)
a+b= 1×2010=2010
