Răspuns :
4+8+12+....+420= 4 x (1+2+3,,,,,+105)= 4 x 105 x (105+1)/2=4 x 105 x 53=22 260
4x(4x1)+(4x2)+(4x3)+.....+(4x105)=4x(1+2+3+.....+105)=4x105x106÷2=2x105x106=210x106=si calculezi
4+8+12+....+420= 4 x (1+2+3,,,,,+105)= 4 x 105 x (105+1)/2=4 x 105 x 53=22 260
4x(4x1)+(4x2)+(4x3)+.....+(4x105)=4x(1+2+3+.....+105)=4x105x106÷2=2x105x106=210x106=si calculezi