Question

B=1/15+1/21=1/28+......+1/190

Answer 1

\(B=2.\left(\frac{1}{30}+\frac{1}{42}+...+\frac{1}{380}\right)\)

\(B=2.\left(\frac{1}{5.6}+\frac{1}{6.7}+...+\frac{1}{19.20}\right)\)

\(B=2.\left(\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+...+\frac{1}{19}-\frac{1}{20}\right)\)

\(B=2.\left(\frac{1}{5}-\frac{1}{20}\right)\)

\(B=2.\frac{3}{20}\)

\(B=\frac{3}{10}\)

Đáp án này là chính xác nhất đó, mình thề. k cho mình nhé

Answer 2

b=2/30+2/42+2/56+...+2/380

Answer 3

\(B=\frac{1}{2}.\left(\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+...+\frac{1}{380}\right)\)

\(B=\frac{1}{2}.\left(\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}+...+\frac{1}{19.20}\right)\)

\(B=\frac{1}{2}.\left(\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+...+\frac{1}{19}-\frac{1}{20}\right)\)

\(B=\frac{1}{2}.\left(\frac{1}{5}-\frac{1}{20}\right)\)

\(B=\frac{1}{2}.\frac{3}{20}\)

\(B=\frac{3}{40}\)

k cho mình nhé

Answer 4

Mk chịu

Answer 5

1+2+3........98+99