Question

Tính:

1.2.3+2.3.4+3.4.5+...+112.113.114

 

Answer 1

A=1.2.3+2.3.4+3.4.5+...+112.113.114

4A= 1.2.3.4+ 3.4.5.4+....+112.113.114.4

4A= 1.2.3.(4-0)+3.4.5.(6-2)+.....+ 112.113.114.(115-111)

4A= 1.2.3.4 - 0.1.2.3 + 3.4.5.6 - 2.3.4.5 +.....+ 112.113.114.115 - 111.112.113.114

4A= 112.113.114.115=165920160

A=165920160:4=41480040

chắc chắn 100% đó

Answer 2

1.2.3+2.3.4+3.4.5+.......+112.113.114=1.2.3.4+2.3.4.4+........+112.113.114.4

                                                      =1.2.3.(5-1)+2.3.4.(6-1)+.................+112.113.114.(115-111)

                                                       =1.2.3-2.3.4+2.3.4-...........................-111.112.113+113.114.115

                                                       =113.114.115/3101

nho k minh nha