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10 tháng 8 2018

\(\left(\dfrac{1}{38}-1\right).\left(\dfrac{1}{37}-1\right).\left(\dfrac{1}{36}-1\right)....\left(\dfrac{1}{2}-1\right)\)

\(=\left(\dfrac{1}{38}-\dfrac{38}{38}\right).\left(\dfrac{1}{37}-\dfrac{37}{37}\right).\left(\dfrac{1}{36}-\dfrac{36}{36}\right)....\left(\dfrac{1}{2}-\dfrac{2}{2}\right)\)

\(=\left(\dfrac{-37}{38}\right).\left(\dfrac{-36}{37}\right).\left(\dfrac{-35}{36}\right)...\left(\dfrac{-1}{2}\right)\)

\(=\left(\dfrac{-1}{38}\right).\left(\dfrac{-1}{1}\right).\left(\dfrac{-1}{1}\right).....\left(-\dfrac{1}{1}\right)\)

\(=\left(\dfrac{-1}{38}\right).\left(-1\right).\left(-1\right).....\left(-1\right)\)

\(=\dfrac{\left(-1\right).\left(-1\right).....\left(-1\right)}{38}\)

\(=\dfrac{\left(-1\right)^{38}}{38}\)

\(=\dfrac{1}{38}\)

27 tháng 7 2018

\(\Rightarrow\dfrac{1}{3}\left(x-\dfrac{3}{2}\right)+\dfrac{1}{2}\left(2x+1\right)=\dfrac{-13}{3}\)

\(\Rightarrow\dfrac{1}{3}x-\dfrac{1}{2}+x+\dfrac{1}{2}=\dfrac{-13}{3}\)

\(\Rightarrow\dfrac{4}{3}x=\dfrac{-13}{3}\Rightarrow x=\dfrac{-13}{4}\)

16 tháng 10 2018

=(1/1+1/3+1/5+1/7+1/9).(1/2+1/4+1/6+1/8+1/10)

=(1+1/3+1/5+1/7+1/9).137/120

=258/315.137/120

=5891/6300

13 tháng 7 2019

\(\left(\frac{1}{38}-1\right).\left(\frac{1}{37}-1\right).\left(\frac{1}{36}-1\right)....\left(\frac{1}{2}-1\right)\)

\(=-\left(1-\frac{1}{38}\right).\left(1-\frac{1}{37}\right)....\left(1-\frac{1}{2}\right)\)

\(=-\frac{37}{38}.\frac{36}{37}...\frac{1}{2}\)

\(=\frac{-1}{38}\)

13 tháng 7 2019

\(\left(\frac{1}{38}-1\right)\left(\frac{1}{37}-1\right)\left(\frac{1}{36}-1\right).......\left(\frac{1}{2}-1\right)\)

\(=\frac{-37}{38}.\frac{-36}{37}.\frac{-35}{36}.......\frac{-2}{3}.\frac{-1}{2}\)

\(=\frac{-1}{38}\)

3 tháng 7 2015

\(=\frac{-37}{38}\cdot\frac{-36}{37}\cdot...\cdot\frac{-1}{2}=\frac{\left(-37\right)\left(-36\right)\cdot...\cdot\left(-1\right)}{38\cdot37\cdot...\cdot2}=\frac{1}{38}\)