tính bằng cách thuan tien :4.2 x 21 +8.4 x 15 +4.2 x48 +4,2
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\(\Leftrightarrow\dfrac{2\cdot3\cdot...\cdot31}{\left(2\cdot3\cdot...\cdot31\right)\cdot\left(2\cdot2\cdot...\cdot2\right)\cdot2^6}=2^x\)
=>2^x=1/2^36
=>x=-36
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(1.2.3.4.5....31)/(2(1.2.3.4.5.....31).64)=2x
1/(2.64)=2x
1/128=2x
2-7=2x
=>x=-7
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\(\dfrac{1}{4}.\dfrac{2}{6}.\dfrac{3}{8}.....\dfrac{31}{64}\)
\(=\dfrac{2.3.....31}{\left(2.3.4.....31\right).\left(2.2.2.....2\right).2^6}\)(Ở phần 2 . 2 . 2 . ... . 2 có 30 số 2)
\(=\dfrac{1}{2^{30+6}}=\dfrac{1}{2^{36}}\)
\(\Rightarrow\dfrac{1}{2^{36}}=2^x\)
\(\Rightarrow2^{36}=2^{0-x}\)
\(\Rightarrow36=0-x\)
\(\Rightarrow x=-36\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Trả lời
\(\frac{1}{4}.\frac{2}{6}.\frac{3}{8}.\frac{4}{10}.....\frac{30}{62}.\frac{31}{64}=2^x\)
\(\Leftrightarrow\frac{1}{2.2.2....2.64}=2^x\) ( 30 số hạng 2 )
\(\Leftrightarrow\frac{1}{2^{30}.2^6}=2^x\)
\(\Leftrightarrow\frac{1}{2^{36}}=2^x\)
\(\Rightarrow2^x=2^{-36}\)
\(\Rightarrow x=-36\)
Vậy \(x=-36\)
![](https://rs.olm.vn/images/avt/0.png?1311)
trả lời đi cần gấp