Question

tính giá trị bieểu thức sau 

\(\frac{5}{1.2}+\frac{5}{2.3}+\frac{5}{3.4}+...+\frac{5}{99.100}\) 

ghi rõ cách làm cho mình nha mình tick cho

Answer 1

\(\text{Ta có: }\frac{5}{1.2}+\frac{5}{2.3}+\frac{5}{3.4}+.....+\frac{5}{99.100}\)

     \(=5.\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+....+\frac{1}{99.100}\right)\)

       \(=5.\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+....+\frac{1}{99}-\frac{1}{100}\right)\)

      \(=5.\left(1-\frac{1}{100}\right)\)

   \(=5.\frac{99}{100}\)

      \(=\frac{99}{20}\)

     

Answer 2

5/1.2 + 5/2.3 + 5/3.4 + ... + 5/99.100

= 5 . ( 1/1.2 + 1/2.3 + 1/3.4 +... + 1/99.100 )

= 5 . ( 1 - 1/2 + 1/2 -1/3 + 1/3 - 1/4 + .... + 1/99 - 1/100 )

= 5 . ( 1 - 1/100 )

= 5 . 99/100

= 99/20

Answer 3

\(\frac{99}{100}\)nhé