Question

tính nhanh

 

. là dấu nhân

\(\frac{2}{11.13}+\frac{2}{13.15}+\frac{2}{15.17}+...+\frac{2}{97.99}\)

Answer 1

mình đoán là 2

Answer 2

\(\frac{2}{11.13}+\frac{2}{13.15}+\frac{2}{15.17}+...+\frac{2}{97.99}\)

\(=\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-\frac{1}{17}+...+\frac{1}{97}-\frac{1}{99}\)

\(=\frac{1}{11}-\frac{1}{99}\)

\(=\frac{9}{99}-\frac{1}{99}=\frac{8}{99}\)

Answer 3

8/99 nha

Nhớ tk mình

Chúc bạn học tốt

^.^

Answer 4

dajshfyygfyagyfe

Answer 5

đáp án là 8/99

Answer 6

8/99 nha bạn

Answer 7

2/11.13 + 2/13.15 + 2/15.17 +.....+2/97.99

=2/2 .( 2/11 - 2/13 + 2/13 -  2/15 + 2/15 - 2/17 +.....+2/97 - 2/99

=2/2.(1/11 - 1/13 +1/13 -1/15 + 1/15 - 1/17 +......+ 1/97 - 1/99

=1.(1/11 - 1/99)

=1. 8/99

=8/99

Answer 8

\(\frac{2}{11.13}+\frac{2}{13.15}+\frac{2}{15.17}+...+\frac{2}{97.99}\)

=\(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+...+\frac{1}{97}-\frac{1}{99}\)

=\(\frac{1}{11}-\frac{1}{99}\)

=\(\frac{8}{99}\)