Question

Tính giá trị biểu thức

\(A=\frac{9}{1.2}+\frac{9}{2.3}+\frac{9}{3.4}+...\frac{9}{98.99}+\frac{9}{99.100}\)

Answer 1

\(A=9\left(\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{99.100}\right)\)

\(=9\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{99}-\frac{1}{100}\right)\)

\(=9\left(1-\frac{1}{100}\right)\)

\(=9\times\frac{99}{100}\)

\(=\frac{891}{100}\)
 

Answer 2

A=9.(1/1.2 +1/2.3 +1/3.4+...+1/98.99 +1/99.100

A=9.(1-1/2+1/2-1/3+1/3-1/4+...+1/98-1/99+1/99-1/100)

A=9.(1-1/100)

A=9.99/100

A=891/100

Answer 3

8.91 k mình mình k lại

Answer 4

A:9=1/1.2+1/2.3+1/3.4+..........+1/98.99+1/99.100

      =1/1-1/2+1/2-1/3+1/3-1/4+........+1/99-1/100

       =1-1/100

       =99/100

=>A=99/100.9

=891/100

 =

Answer 5

\(A=9.\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+......+\frac{1}{99}-\frac{1}{100}\right)\)

\(A=9.\left(1-\frac{1}{100}\right)\)

\(A=9.\frac{99}{100}=\frac{891}{100}\)