Question

\(\frac{1}{3\cdot7}+\frac{1}{7\cdot11}+...+\frac{1}{23\cdot27}\)

Answer 1

= \(\frac{1}{3}-\frac{1}{27}\)

= \(\frac{9}{27}-\frac{1}{27}\)

= \(\frac{8}{27}\)

Answer 2

1/3.7 + 1/7.11 + ... + 1/23.27

= 1/3 - 1/7+ 1/7 - 1/11 + ... + 1/23 - 1/27

= 1/3 -1/27

= 8/27

Kết mk nha

Answer 3

\(\frac{1}{3.7}+\frac{1}{7.11}+...+\frac{1}{23.27}\)

\(=\frac{1}{4}.\left(\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+...+\frac{1}{23}-\frac{1}{27}\right)\)

\(=\frac{1}{4}.\left(\frac{1}{3}-\frac{1}{27}\right)\)

\(=\frac{1}{4}\cdot\frac{8}{27}=\frac{2}{27}\)

Answer 4

=1/4.(4/3.7+4/7.11+...+4/23.27

=1/4.(1/3-1/7+1/7-1/11+...+1/23-1/27

=1//4.(1/3-1/27)

=1/4.8/27

=2/27