Question

s=1.2+2.3+3.4+....+99.100 giup minh voi

Answer 1

s=1.2+2.3+3.4+...+99.100

=>3s=1.2.3+2.3.3+3.4.3+...+99.100.3

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

=1.2.3-1.2.3+2.3.4-2.3.4+...-98.99.100+99.100.101

=99.100.101

=>s=99.100.101/3=333300