Question

tính

\(A=1.4+2.5+3.6+.....+99.102\)

Answer 1

https://olm.vn/hoi-dap/question/271984.html

Answer 2

\(A=1.4+2.5+3.6+....+99.102\)

\(A=1.\left(1+3\right)+2.\left(2+3\right)+3.\left(3+3\right)+...+99\left(99+3\right)\)

\(A=1^2+1.3+2^2+2.3+3^2+3.3+....+99^2+99.3\)

\(A=\left(1^2+2^2+......+99^2\right)+\left(1.3+2.3+.....+99.3\right)\)

\(A=\left(1^2+2^2+...+99^2\right)+3\left(1+2+....+99\right)\)

Làm tiếp nhé :(