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\(A=\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}\)
\(A=\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}\)
\(A=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}\)
\(A=\frac{1}{2}-\frac{1}{8}\)
\(A=\frac{3}{8}\)
\(A=\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}\)
\(A=\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}\)
\(A=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}\)
\(A=\frac{1}{2}-\frac{1}{8}=\frac{3}{8}\)
mình nhé!
Ta có :
\(A=\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{9900}\)
\(A=\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{99.100}\)
\(A=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{99}-\frac{1}{100}\)
\(A=\frac{1}{2}-\frac{1}{100}\)
\(A=\frac{49}{100}\)
Chúc bạn học tốt ~
\(A=\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{9900}\)
\(\Leftrightarrow A=\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+\frac{1}{4\cdot5}+...+\frac{1}{99\cdot100}\)
\(\Leftrightarrow A=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+....+\frac{1}{99}-\frac{1}{100}\)
\(\Leftrightarrow A=\frac{1}{2}-\frac{1}{100}\)
\(\Leftrightarrow A=\frac{49}{100}\)
Vậy A=\(\frac{49}{100}\)
\(\text{ta có:}\frac{6}{a\left(a+7\right)}+1=\frac{\left(a+1\right)\left(a+6\right)}{a\left(a+7\right)}\text{ do đó:}A=\frac{2.7}{1.8}.\frac{3.8}{2.9}.....\frac{101.106}{100.107}\)
\(=\frac{2.3...101.\left(7.8....106\right)}{1....101.\left(8.9.....107\right)}=\frac{7}{107}\)
Bài làm
\(D=\frac{6}{3,5}+\frac{6}{5.7}+...+\frac{6}{21.23}\)
\(D=3.\left(\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{21.23}\right)\)
\(D=3.\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{21}-\frac{1}{23}\right)\)
\(D=3.\left(\frac{1}{3}-\frac{1}{23}\right)\)
\(D=3.\frac{20}{69}\)
\(D=\frac{20}{23}\)
Học tốt
Bài làm
\(D=\frac{6}{3.5}+\frac{6}{5.7}+...+\frac{6}{21.23}\)
\(D=3.\left(\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{21.23}\right)\)
\(D=3.\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{21}-\frac{1}{23}\right)\)
\(D=3.\left(\frac{1}{3}-\frac{1}{23}\right)\)
\(D=3.\frac{20}{69}\)
\(D=\frac{20}{23}\)
\(E=\frac{20}{11.13}+\frac{20}{13.15}+\frac{20}{15.17}+...+\frac{20}{53.55}\)
\(E=10.\left(\frac{2}{11.13}+\frac{2}{13.15}+\frac{2}{15.17}+...+\frac{2}{53.55}\right)\)
\(E=10.\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-\frac{1}{17}+...+\frac{1}{53}-\frac{1}{55}\right)\)
\(E=10.\left(\frac{1}{11}-\frac{1}{55}\right)\)
\(E=10.\frac{4}{55}\)
\(E=\frac{8}{11}\)
\(G=\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+...+\frac{1}{9900}\)
\(G=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+...+\frac{1}{99.100}\)
\(G=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+...+\frac{1}{99}-\frac{1}{100}\)
\(G=\frac{1}{1}-\frac{1}{100}\)
\(G=\frac{99}{100}\)
Nhớ k cho m nha
2E=1+\(\frac{1}{2}+\frac{1}{2^2}+...+\frac{1}{2^{2003}}\)
2E-E=1-\(\frac{1}{2^{2004}}\)
E=\(\frac{1}{2^{2004}}\)
Ủng hộ mk nha
Bài 1 mik học xong quên hết òi (mấy bài kia là hok biết luôn :V)
mk chỉ cần nhìn sơ qua là biết có câu dễ sao bn ko tự nghĩ đi hơi dễ rồi trừ khi bn đố tôi chục câu tiếng anh vật lí văn
M=1/6+1/12+1/20+..+1/2009.2010
M=1/2.3+1/3.4+1/4.5+...+1/2009.2010
M=1/2-1/3+1/3-1/4+1/4-1/5+...+1/2009-1/2010
M=1/2-1/2010
M=1004/2010
Tự rút gọn bn nha
M=1/6+=1/12+1/20+......+1/2009.2010]
M=1/2.3+1/3.4+1/4.5+.........+1/2009.2010
M=1/2-1/3+1/3-1/4+1/4-1/5+........+1/2009-1/2010
M=1/2-1/2010
=502/1005