Question

[Nguyễn Thị Thùy linh]

giải hộ với:

C= 1x2x3+2x3x4+...........+8x9x10

Answer 1

[Đức Phạm]

\(C=1.2.3+2.3.4+...+8.9.10\)

\(4C=1.2.3.4+2.3.4.4+...+8.9.10.4\)

\(4C=1.2.3.\left(4-0\right)+2.3.4.\left(5-1\right)+...+8.9.10.\left(11-7\right)\)

\(4C=1.2.3.4+2.3.4.5+....+8.9.10.11\)

\(\Rightarrow C=\frac{8.9.10.11}{4}=1980\)

Answer 2

[»βέ•Ҫɦαηɦ«]

Ta có : C = 1 x 2 x 3 + 2 x 3 x 4 +...........+ 8 x 9 x 10

=> 4C = 1.2.3.4 - 1.2.3.4 + 2.3.4.5 - 2.3.4.5 + ..... + 8.9.10.11

=> 4C = 8.9.10.11

=> C = \(\frac{8.9.10.11}{4}=1980\)