Question

Tính A=1.3+2.4+3.5+....+99.101

Answer 1

A=1(2+1)+2(3+1)+3(4+1)+...+99(100+1)

A=1.2+1+2.3+2+3.4+3+...+99.100+99

A=1.2+2.3+3.4+...+99.100)+(1+2+3+...+99)

A=333300+4950=338250