Question

Tinh gia tri cac bieu thuc sau

B= \(\frac{10}{2.7}+\frac{10}{7.12}+...+\frac{10}{502.507}\)

C=  \(\frac{1}{18}+\frac{1}{54}+\frac{1}{108}+...+\frac{1}{990}\)

Answer 1

hello

Answer 2

6/u

trrtu

Answer 3

\(B=\frac{10}{2.7}+\frac{10}{7.12}+...+\frac{10}{502.507}\)

\(B=2.\left(\frac{5}{2.7}+\frac{5}{7.12}+...+\frac{5}{502.507}\right)\)

\(B=2.\left(\frac{1}{2}-\frac{1}{7}+\frac{1}{7}-\frac{1}{12}+...+\frac{1}{502}-\frac{1}{507}\right)\)

\(B=2.\left(\frac{1}{2}-\frac{1}{507}\right)\)

\(B=2.\frac{505}{1014}\)
\(B=\frac{505}{507}\)

Answer 4

\(B=\frac{10}{2.7}+\frac{10}{7.12}+...+\frac{10}{502.507}\)

\(B=2.\left(\frac{5}{2.7}+\frac{5}{7.12}+...+\frac{5}{502.507}\right)\)

\(B=2.\left(\frac{1}{2}-\frac{1}{7}+\frac{1}{7}-\frac{1}{12}+...+\frac{1}{502}-\frac{1}{507}\right)\)

\(B=2.\left(\frac{1}{2}-\frac{1}{507}\right)\)

\(B=2.\frac{505}{1014}\)

\(B=\frac{505}{507}\)

    \(C=\frac{1}{18}+\frac{1}{54}+\frac{1}{108}+...+\frac{1}{990}\)

\(C=\frac{1}{3.6}+\frac{1}{6.9}+\frac{1}{9.12}+...+\frac{1}{30.33}\)

\(C=\frac{1}{3}.\left(\frac{3}{3.6}+\frac{3}{6.9}+\frac{3}{9.12}+...+\frac{3}{30.33}\right)\)

\(C=\frac{1}{3}.\left(\frac{1}{3}-\frac{1}{6}+\frac{1}{6}-\frac{1}{9}+\frac{1}{9}-\frac{1}{12}+...+\frac{1}{30}-\frac{1}{33}\right)\)

\(C=\frac{1}{3}.\left(\frac{1}{3}-\frac{1}{33}\right)\)

\(C=\frac{1}{3}.\frac{10}{33}\)

\(C=\frac{10}{99}\)