Răspuns :
faci 52-4=48 termeni
S=5+6+7.....+51+52
S=52+51+....+7+6+5
2xS= 48 x 57
S=(48x57):2
S= 24x57
S=1368
S=5+6+7.....+51+52
S=52+51+....+7+6+5
2xS= 48 x 57
S=(48x57):2
S= 24x57
S=1368