Question

Tính nhanh giá trị biểu thức  

1/1+1/6+1/12+....+1/90

Answer 1

\(\frac{1}{1}+\frac{1}{6}+\frac{1}{12}+....+\frac{1}{90}\)

\(=\frac{1}{1}+\left(\frac{1}{6}+\frac{1}{12}+....+\frac{1}{90}\right)\)

\(=\frac{1}{1}+\left(\frac{1}{2.3}+\frac{1}{3.4}+.....+\frac{1}{9.10}\right)\)

\(=1+\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+....+\frac{1}{9}-\frac{1}{10}\right)\)

\(=1+\left(\frac{1}{2}-\frac{1}{10}\right)\)

\(=1+\frac{2}{5}=\frac{7}{5}\)

Answer 2

7/5 nha bn

Answer 3

 = \(\frac{7}{5}\)nha bạn yêu , còn cách làm thì mk làm giống như Kurosaki Akatsu !!!!

Answer 4

7/5 nha

Answer 5

7/5 nha

Answer 6

1/1+(1/6+1/12+...+1/90)

=1+(1/2.3+1/3.4+...+1/9.10)

=1+(1/2-1/3+1/3-1/4+...+1/9-1/10)

=1+(1/2-1/10)

=1+2/5

=7/5