Bài 5:
- \(A=\dfrac{2^2}{3}.\dfrac{3^2}{8}.\dfrac{4^2}{15}.\dfrac{5^2}{24}.\dfrac{6^2}{35}.\dfrac{7^2}{48}.\dfrac{8^2}{63}.\dfrac{9^2}{80}\)
\(=\dfrac{2^2}{3}.\dfrac{3^2}{2.4}.\dfrac{4^2}{3.5}.\dfrac{5^2}{4.6}.\dfrac{6^2}{5.7}.\dfrac{7^2}{6.8}.\dfrac{8^2}{7.9}.\dfrac{9^2}{8.10}\)
\(=\dfrac{2^2.3^2.4^2.5^2.6^2.7^2.8^2.9^2}{3.2.4.3.5.4.6.5.7.6.8.7.9.8.10}\)
\(=\dfrac{2^2.3^2.4^2.5^2.6^2.7^2.8^2.9^2}{2.3^2.4^2.5^2.6^2.7^2.8^2.9.10}\)
\(=\dfrac{9}{5}\)
- \(B=\dfrac{8}{9}.\dfrac{15}{16}.\dfrac{24}{25}...\dfrac{2499}{2500}\)
\(=\dfrac{2.4}{3^2}.\dfrac{3.5}{4^2}.\dfrac{4.6}{5^2}...\dfrac{49.51}{50^2}\)
\(=\dfrac{2.4.3.5.4.6...49.51}{3^2.4^2.5^2...50^2}\)
\(=\dfrac{2.51}{3.50}\)
\(=\dfrac{17}{25}\)
- \(C=\left(1+\dfrac{8}{10}\right)\left(1+\dfrac{8}{22}\right)\left(1+\dfrac{8}{36}\right)...\left(1+\dfrac{8}{8352}\right)\)
\(=\dfrac{18}{10}.\dfrac{30}{22}.\dfrac{44}{36}...\dfrac{8360}{8352}\)
\(=\dfrac{2.9}{10}.\dfrac{3.10}{2.11}.\dfrac{4.11}{3.12}...\dfrac{88.95}{87.96}\)
\(=\dfrac{2.9.3.10.4.11...88.95}{10.2.11.3.12...87.96}\)
\(=\dfrac{9.88}{96}\)
\(=\dfrac{3}{4}\)
giúp mk với, mk cần gấp ạ. camon mn rất nhìu, giải chi tiết dễ hiểu giúp mk nha
Giúp mk câu 1 với mk cần gấp, cảm ơn mn rất nhiều
giúp mk với, mk cần gấp, mn nêu cả lời giải chi tiêt 1 chút giúp mk nhé, cam on mn rất nhìu ạ
