Question

1*2+3*4+5*6+...+99*100

Answer 1

=>3S + 1.2.3+2.3.3+...+99.100.3

=>1.2.3+2.3(4-1)+3.4(5-2)+...+99.100(101-98)

=>1.2.3+2.3.4-1.2.3+3.4.5+-2.3.4+...+99.100.101-98.100.101

=>99.100.101=999900

=>S=333300

tick nhé

Answer 2

kho....................wa..................troi.......................thi.....................ret.................lanh................wa..................tich............................ung.........................ho..............minh......................cho....................do....................lanh