Ai giải giúp mình câu này với 1+1-1+1-1*1/1*1/1/1*1+1+1+1-1-1-1/1*1-1-1+1+1
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`1/2 xx 1/3 xx 1/4`
`= (1xx1xx1)/(2xx3xx4)`
`= 1/24`
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`1/2 xx 1/3 : 1/4`
`= 1/2 xx 1/3 xx 4`
`= (1xx1xx4)/(2xx3)`
`= 4/6`
`=2/3`
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`1/2 : 1/3 xx1/4`
`= 1/2 xx 3 xx 1/4`
`=(1xx3xx1)/(2xx4)`
`= 3/8`
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`1/2 : 1/3 : 1/4`
`= 1/2 xx 3xx4`
`= 12/2`
`=6`
`1/2xx1/3xx1/4`
`=1/24`
`1/2xx1/3:1/4`
`=1/6xx4`
`=4/6=2/3`
`1/2:1/3xx1/4`
`=1/2xx3xx1/4`
`=3/2xx1/4`
`=3/8`
`1/2:1/3:1/4`
`=1/2xx3xx4`
`=6`
= 1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/7-1/8+1/8-1/9
=1/2-1/9
= 7/18
\(\frac{1}{11×14}+\frac{1}{14×17}+\frac{1}{17×20}+\frac{1}{20×23}+\frac{1}{23×26}\)
\(=\frac{1}{3}×\left(\frac{3}{11×14}+\frac{3}{14×17}+\frac{3}{17×20}+\frac{3}{20×23}+\frac{3}{23×26}\right)\)
\(=\frac{1}{3}×\left(\frac{1}{11}-\frac{1}{14}+\frac{1}{14}-\frac{1}{17}+...+\frac{1}{23}-\frac{1}{26}\right)\)
\(=\frac{1}{3}×\left(\frac{1}{11}-\frac{1}{26}\right)\)
\(=\frac{1}{3}×\frac{15}{286}\)
\(=\frac{5}{286}\)
\(\frac{1}{11\times14}+\frac{1}{14\times17}+\frac{1}{17\times20}+\frac{1}{20\times23}+\frac{1}{23\times26}\)
\(=\frac{1}{3}\times\left(\frac{1}{11\times14}+\frac{1}{14\times17}+\frac{1}{17\times20}+\frac{1}{20\times23}+\frac{1}{23\times26}\right)\)
\(=\frac{1}{3}\times\left(\frac{1}{11}-\frac{1}{14}+\frac{1}{14}-\frac{1}{17}+\frac{1}{17}-\frac{1}{20}+\frac{1}{20}-\frac{1}{23}+\frac{1}{23}-\frac{1}{26}\right)\)
\(=\frac{1}{3}\times\left(\frac{1}{11}-\frac{1}{26}\right)\)
= 5/286
Đặt \(A=\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+...+\frac{1}{1024}\)
\(2A=1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+...+\frac{1}{1024}\)
\(2A-A=\left(1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+...+\frac{1}{1024}\right)-\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+...+\frac{1}{1024}\right)\)
\(\Rightarrow A=1-\frac{1}{1024}=\frac{1023}{1024}\)
Ai giúp mình câu này với
(1+1/2+1/3+...+1/2012+1/2013) .x +2013 = 2014+2015/2+...+4025/2012+4026/2013
\(-3+\frac{1}{1+\frac{1}{3+\frac{1}{1+\frac{1}{3}}}}\)
\(=-3+\frac{1}{1+\frac{1}{3+\frac{3}{4}}}\)
\(=-3+\frac{1}{1+\frac{4}{15}}\)
\(=-3+\frac{15}{19}\)
\(=-\frac{42}{19}\)
\(A=\dfrac{1}{5}+\dfrac{1}{10}+\dfrac{1}{20}+\dfrac{1}{40}+\dfrac{1}{80}+\dfrac{1}{160}\\ A=\dfrac{35}{160}+\dfrac{16}{160}+\dfrac{8}{160}+\dfrac{4}{160}+\dfrac{2}{160}+\dfrac{1}{160}\\ A=\dfrac{66}{160}\\ A=\dfrac{33}{80}.\)
B = 1+1³+1⁴+...+1⁹⁸+1⁹⁹
B1 = 1³+1⁵+...+1⁹⁹+1¹⁰⁰
B1-B =(1³+1⁵+...+1⁹⁹+1¹⁰⁰) - ( 1+1³+1⁴+...+1⁹⁸+1⁹⁹ )
B0 = 1¹⁰⁰ - 1⁹⁹
B = 1
=1
Khá đơn giản