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PA
1
NT
Nguyễn Thị Thương Hoài
Giáo viên
VIP
20 tháng 3 2023
A = (1+1) \(\times\) (1+\(\dfrac{1}{2}\)) \(\times\) (1+\(\dfrac{1}{3}\)) \(\times\)....\(\times\)(1+ \(\dfrac{1}{2020}\))
A = 2 \(\times\) \(\dfrac{3}{2}\) \(\times\) \(\dfrac{4}{3}\) \(\times\) \(\dfrac{5}{4}\) \(\times\).......\(\times\) \(\dfrac{2021}{2020}\)
A =\(\dfrac{2\times3\times4\times....\times2020}{2\times3\times4\times....\times2020}\) \(\times\) \(\dfrac{2021}{1}\)
A = 1 \(\times\) 2021
A = 2021
15 tháng 5 2022
\(F=1\dfrac{1}{5}\times1\dfrac{1}{6}\times1\dfrac{1}{7}\times\cdot\cdot\cdot\times1\dfrac{1}{2019}\times1\dfrac{1}{2020}\)
\(F=\dfrac{6}{5}\times\dfrac{7}{6}\times\dfrac{8}{7}\times\cdot\cdot\cdot\times\dfrac{2020}{2019}\times\dfrac{2021}{2020}\)
\(F=\dfrac{6\times7\times8\times\cdot\cdot\cdot\times2020\times2021}{5\times6\times7\times\cdot\cdot\cdot\times2019\times2020}\)
\(F=\dfrac{2021}{5}\)
| \(Huyền\) |
C
15 tháng 5 2022
\(f=1^1_5\times1^1_6\times1^1_7\times......\times1^1_{2019}\times1^1_{2022}\)
\(f=\dfrac{6}{5}\times\dfrac{7}{6}\times\dfrac{8}{7}\times....\times\dfrac{2020}{2019}\times\dfrac{2021}{2020}\)
\(f=\dfrac{6\times7\times8\times....\times2020\times2021}{5\times6\times7\times.....\times2019\times2020}\)
\(f=\dfrac{2021}{5}\)
\(#Tarus\)
BD
15 tháng 6 2023
\(\dfrac{2}{5}\times\dfrac{1}{7}+\dfrac{2}{7}\times\dfrac{2}{5}\)
\(=\dfrac{2}{5}\times\left(\dfrac{1}{7}+\dfrac{2}{7}\right)\)
\(=\dfrac{2}{5}\times\dfrac{3}{7}\)
\(=\dfrac{6}{35}\)
\(x+\dfrac{1}{2}\times\dfrac{1}{3}=\dfrac{3}{4}\)
\(x+\dfrac{1}{6}=\dfrac{3}{4}\)
\(x=\dfrac{9}{12}-\dfrac{2}{12}\)
\(x=\dfrac{7}{12}\)
\(\left(1-\dfrac{1}{2}\right)\times\left(1-\dfrac{1}{3}\right)\times\left(1-\dfrac{1}{4}\right)\times...\times\left(1-\dfrac{1}{2020}\right)+x=\dfrac{1}{2}\)
\(\dfrac{1}{2}\times\dfrac{2}{3}\times\dfrac{3}{4}\times...\times\dfrac{2019}{2020}+x=\dfrac{1}{2}\)
\(\dfrac{1}{2020}+x=\dfrac{1}{2}\)
\(x=\dfrac{1}{2}-\dfrac{1}{2020}\)
\(x=\dfrac{1010}{2020}-\dfrac{1}{2020}\)
\(x=\dfrac{1009}{2020}\)
H9
HT.Phong (9A5)
CTVHS
15 tháng 6 2023
\(\dfrac{2}{5}\times\dfrac{1}{7}+\dfrac{2}{7}\times\dfrac{2}{5}\)
\(=\dfrac{2}{5}\times\left(\dfrac{1}{7}+\dfrac{2}{7}\right)\)
\(=\dfrac{2}{5}\times\dfrac{3}{7}\)
\(=\dfrac{6}{35}\)
\(x+\dfrac{1}{2}\times\dfrac{1}{3}=\dfrac{3}{4}\)
\(\Rightarrow\dfrac{1}{2}\times\dfrac{1}{3}=\dfrac{3}{4}-x\)
\(\Rightarrow\dfrac{3}{4}-x=\dfrac{1}{6}\)
\(\Rightarrow x=\dfrac{3}{4}-\dfrac{1}{6}=\dfrac{7}{12}\)
\(\left(1-\dfrac{1}{2}\right)\times\left(1-\dfrac{1}{3}\right)\times\left(1-\dfrac{1}{4}\right)\times...\times\left(1-\dfrac{1}{2020}\right)+x=\dfrac{1}{2}\)
\(\Rightarrow\dfrac{1}{2}\times\dfrac{2}{3}\times\dfrac{3}{4}\times...\times\dfrac{2019}{2020}+x=\dfrac{1}{2}\)
\(\Rightarrow\dfrac{1\times2\times3\times4\times...\times2019}{2\times3\times4\times5\times...\times2020}+x=\dfrac{1}{2}\)
\(\Rightarrow\dfrac{1}{2020}+x=\dfrac{1}{2}\)
\(\Rightarrow x=\dfrac{1}{2}-\dfrac{1}{2020}=\dfrac{1009}{2020}\)
NN
Nguyễn Ngọc Anh Minh
CTVHS
VIP
7 tháng 4 2020
A=1/2x2/3x3/4x...x2018/2019x2019/2020=1/2020
19 tháng 7 2022
A = 1/2 x 2/3 x 3/4 x ... x 2018/2019 x 2019/2020 = 1/2020