Question

[ngo mai phuong]

A=1.2+2.3+3.4+..........+99.100

B=1.3+3.5+5.7+...........+97.99

C=1.2.3+2.3.4+............98.99.100

Answer 1

[Nguyễn Đình Dũng]

A = 1.2. + 2.3 + 3.4 + ... + 99.100

3A = 1.2.3 + 2.3.(4-1) + ... + 99.100.(101-98)

3A = 1.2.3 + 2.3.4 - 2.3.1 + ... + 99.100.101 - 99.100.98

3A = 99.100.101

3A = 999900

A = 333300