Question

tính nhanh

m= 1x2+2x3+3x4+...+201x202

Answer 1

mn giúp mình với ạ !

Answer 2

\(\Rightarrow3M=1.2.3+2.3.3+...+201.202.3\)

              \(=1.2.3+2.3.\left(4-1\right)+...+201.202.\left(203-200\right)\)

              \(=1.2.3+2.3.4-1.2.3+...+201.202.203-200.201.202\)

                \(=201.202.203\)

\(\Rightarrow M=\frac{201.202.203}{3}\)