Tinh gia tri cac bieu thuc sau
B= \(\frac{10}{2.7}+\frac{10}{7.12}+...+\frac{10}{502.507}\)
C= \(\frac{1}{18}+\frac{1}{54}+\frac{1}{108}+...+\frac{1}{990}\)
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Tinh giai tri cac bieu thuc sau
F = \(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+...+\frac{1}{190}\)
\(\frac{F}{2}=\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{380}\)
\(\frac{F}{2}=\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{19.20}\)
\(\frac{F}{2}=\frac{3-2}{2.3}+\frac{4-3}{3.5}+\frac{5-4}{4.5}+...+\frac{20-19}{19.20}\)
\(\frac{F}{2}=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{19}-\frac{1}{20}\)
\(\frac{F}{2}=\frac{1}{2}-\frac{1}{20}=\frac{9}{20}\Rightarrow F=\frac{18}{20}=\frac{9}{10}\)
tinh gia tri bieu thuc a = \(\sqrt{4+\sqrt[3]{8}+\frac{2}{3}}+3^{10}\frac{1}{1\times2}+\frac{1}{2\times3}+...+\frac{1}{99\times100}\)
tinh gia tri bieu thuc a = \(\sqrt{4+\sqrt[3]{8+\frac{2}{3}+3^{10}}\frac{1}{1\times2}+\frac{1}{2\times3}+...+\frac{1}{99\times100}}\)
tinh gia tri bieu thuc a = \(\sqrt{4+\sqrt[3]{8}+\frac{2}{3}+3^{10}}\frac{1}{1\times2}+\frac{1}{2\times3}+...+\frac{1}{99\times100}\)
tinh gia tri bieu thuc a = \(\sqrt{4+\sqrt[3]{8+\frac{2}{3}+3^{10}\frac{1}{1\times2}+\frac{1}{2\times3}+...+\frac{1}{99\times100}}}\)
tinh gia tri bieu thuc a = \(\sqrt{4+\sqrt[3]{8+\frac{2}{3}+3^{10}\frac{1}{1\times2}+\frac{1}{2\times3}+...+\frac{1}{99\times100}}}\)
tinh gia tri bieu thuc a = \(\sqrt{4+\sqrt[3]{8+\frac{2}{3}+3^{10}\frac{1}{1\times2}+\frac{1}{2\times3}+...+\frac{1}{99\times100}}}\)
tinh gia tri bieu thuc a = \(\sqrt{4+\sqrt[3]{8+\frac{2}{3}+3^{10}}\frac{1}{1\times2}+\frac{1}{2\times3}+...+\frac{1}{99\times100}}\)
Tinh gia tri cac bieu thuc sau
a) A = \(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{49.50}\)
\(A=\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+...+\frac{1}{49\cdot50}\)
\(A=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{49}-\frac{1}{50}\)
\(A=\frac{1}{1}-\frac{1}{50}\)
\(A=\frac{49}{50}\)
\(A=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{49.50}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{49}-\frac{1}{50}\)
\(=1-\frac{1}{50}=\frac{49}{50}\)