Question

1/2+1/6+1/12+1/20+...+1/90+1/110+1/132

mk giải như thề này đ ko ạ

Answer 1

Là sao mik chả hỉu gì cả??????

Answer 2

Ta có : \(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{90}+\frac{1}{110}+\frac{1}{132}\)

= \(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{9.10}+\frac{1}{10.11}+\frac{1}{11.12}\)

= \(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{9}-\frac{1}{10}+\frac{1}{10}-\frac{1}{11}+\frac{1}{11}-\frac{1}{12}\)

= \(1-\frac{1}{12}=\frac{11}{12}\)

Answer 3

1/2 + 6/ 1 + 12/ 1 + ......... + 1/132 = 1/ 1.2  + 1/2.3  + 1/3.4  + .......... +1/ 11.12  = 1 − 1/2  + 1/'2  − 1/3  + 1/3  − 1/4  + ........... + 1/11  − 1/12  = 1 − 1/12  = 11/12