Răspuns :
a= 0,1,2,3,4,5,6,7,8,9
231+232+.......+238+239=?
239• ( 239+1):2=
239•240:2
239•120=28680
231+232+.......+238+239=?
239• ( 239+1):2=
239•240:2
239•120=28680