Question

tính \(\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{99.100}\)

Answer 1

đặt cái trên là A

=> A=\(\frac{2-1}{1.2}+\frac{3-2}{3.2}+..+\frac{100-99}{100.99}\)

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

=1-1/100=99/100

Answer 2

\(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{99.100}\)

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

\(=1-\frac{1}{100}=\frac{99}{100}\)

Answer 3

\(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{99.100}\)

\(=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{99}-\frac{1}{100}\)

\(=\frac{1}{1}-\frac{1}{100}=\frac{99}{100}\)

Answer 4

\(\frac{1}{1.2}+\frac{1}{2.3}+....+\frac{1}{99.100}\)

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

= 1.(\(\frac{1}{1}-\frac{1}{100}\))

= 1.\(\frac{99}{100}\)

= \(\frac{99}{100}\)

Chúc bạn học tốt 

Answer 5

bài dễ thế này mà ko ai làm à

Answer 6

à mấy bn cho mk xin dấu hiệu chia hết 7

Answer 7

A

Answer 8

đáp án A