1x2+2x3+3x4+...+98x99+99x100 = ?
Tinh : 1x2+2x3+3x4+...+99x100
1X2+2X3+3X4+..........+99X100+100X101
M=1x2+2x3+3x4+4x5+....+99x100
Tính tổng:
A = 1x2+3x4+4x5+...+99x100
B = 1x22+2x32+3x42+4x52+...+99x1002
Tính tổng: A = 1x2 + 2x3 + 3x4+...+99x100
Tinhs tổng S=1x2+2x3+3x4+...+99x100
Tính A= 1x2+2x3+3x4+...+99x100
tính tổng:S= 1x2 + 2x3 + 3x4 + 4x5 +...+ 99x100