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a: \(=\dfrac{20\left(1-12\right)}{30\left(-1-10\right)}=\dfrac{2}{3}\)
b: \(=\dfrac{11^9\cdot3^{18}}{3^{18}\cdot11^{11}}=\dfrac{1}{121}\)
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a: \(=\dfrac{20\left(1-12\right)}{30\left(-1-10\right)}=\dfrac{20}{30}=\dfrac{2}{3}\)
b: \(=\dfrac{11^9\cdot3^{18}}{3^{10}\cdot11^{11}\cdot3^8}=\dfrac{1}{121}\)
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1:
a: Vì \(\dfrac{-4}{3}=\dfrac{-4\cdot3}{3\cdot3}=\dfrac{-12}{9}=\dfrac{12}{9}\\ \Rightarrow\dfrac{-4}{3}=\dfrac{12}{9}\)
b: Vì : \(-2\cdot3=-6\\ -6\cdot8=-48\)
nên 2 p/s ko bằng nhau
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a) `(-63)/72 = (-63:9)/(72:9)=(-7)/8`
b) `20/(-140) = (20:20)/(-140:20) = 1/(-7)=(-1)/7`
c) `(3.10)/(5.24) =(3.2.5)/(5.2 .3.4)=1/4`
d) `(6.5-6.2)/(6+3)=18/9=2`
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`a, (4x+5) : 3 -121:11=14`
`=> (4x+5) : 3 - 11=14`
`=> (4x+5) : 3 =14+11`
`=> (4x+5) : 3 = 25`
`=> 4x+5=25xx3`
`=>4x+5= 75`
`=> 4x=75-5`
`=>4x=70`
`=>x= 70/4`
`=>x= 35/2`
`b, 2+4+6+...+x=2450`
Số lượng của dãy là :
`(x-2)/2 + 1= (x-2)/2 +2/2= x/2`
Tổng số lượng là :
\(\dfrac{\left(x+2\right)\cdot\dfrac{x}{2}}{2}=\dfrac{\dfrac{x^2}{2}+\dfrac{2x}{2}}{2}=\dfrac{x\left(x+2\right)}{4}\)
\(\dfrac{x\left(x+2\right)}{4}=2450\)
\(\Rightarrow x\left(x+2\right)=2450\cdot4\\ \Rightarrow x\left(x+2\right)=9800\)
`=>x=98`
`c,` `1` nhân `32` sao?
`d, 2x+3x=1505`
`=> (2+3)x=1505`
`=> 5x=1505`
`=> x= 1505:5`
`=>x= 301`
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\(C=\dfrac{1}{2}+\dfrac{1}{2^2}+\dfrac{1}{2^3}+...+\dfrac{1}{2^{2020}}\\ 2C=1+\dfrac{1}{2}+\dfrac{1}{2^2}+...+\dfrac{1}{2^{2019}}\\ 2C-C=\left(1+\dfrac{1}{2}+\dfrac{1}{2^2}+...+\dfrac{1}{2^{2019}}\right)-\left(\dfrac{1}{2}+\dfrac{1}{2^2}+\dfrac{1}{2^3}+...+\dfrac{1}{2^{2020}}\right)\\ C=1-\dfrac{1}{2^{2020}}=\dfrac{2^{2020}-1}{2^{2020}}\)
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Giải:
C=1/2 + 1/2^2 + 1/2^3 + ... + 1/2^2020
2C=1 + 1/2 + 1/2^2 + ... +1/2^2019
2C-C=(1+1/2+1/2^2+...+1/2^2019)-(1/2+1/2^2+1/2^3+...+1/2^2020)
C=1-1/2^2020
Chúc bạn học tốt!
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`a) (243756000)/(-487512000)=243756000/(-2.243756000)=1/(-2)=(-1)/2`
`b) (3.16-3.14)/(-12)=(3.2)/(3.(-4))=2/(-4)=(-1)/2`
`c) (-8.4+8.3)/(8.6-8.4)=(-8)/(8.2)=(-1.8)/(2.8)=(-1)/2`
`d) (-15)/(-90)=(-15.1)/(-15.6)=1/6`