Cần gấp bài nào nói rõ ra nhé, ko phải lúc nào cũng đăng `1` lần cả chục câu đâu bn ?
Bài `6` :
`2/3 x + 5/7 = 3/10`
`2/3 x = 3/10 - 5/7`
`2/3 x = -29/70`
`x=-29/70 : 2/3`
`x=-29/70 xx 3/2`
`x=-87/140`
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`3/4 x - 1/2 = 3/7`
`3/4 x = 3/7 +1/2`
`3/4 x = 6/14 + 7/14`
`3/4 x = 13/14`
`x=13/14 : 3/4`
`x=13/14 xx 4/3`
`x=26/21`
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Bài `7` :
`1/2 x + 3/5x = -33/25`
`(1/2 + 3/5)x = -33/25`
`(5/10 + 6/10) x = -33/25`
`11/10 x = -33/25`
`x=-33/25 : 11/10`
`x=-33/25 xx 10/11`
`x=-6/5`
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`(2/3x - 4/9).(1/2 + (-3)/7 : x)=0`
`@TH1:`
`2/3 x - 4/9=0`
`2/3 x = 0 +4/9`
`2/3 x= 4/9`
`x=4/9 : 2/3`
`x=4/9 xx 3/2`
`x=2/3`
`@TH2:`
`1/2 + (-3/7) : x = 0`
`1/2 - 3/7 : x = 0`
`3/7 : x =1/2 - 0`
`3/7 : x = 1/2`
`x=3/7 : 1/2`
`x=3/7 xx 3`
`x=6/7`
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\(\dfrac{x+5}{2005}+\dfrac{x+6}{2004}+\dfrac{x+7}{2003}=-3\)
\(\Leftrightarrow\left(\dfrac{x+5}{2005}+1\right)+\left(\dfrac{x+6}{2004}+1\right)+\left(\dfrac{x+7}{2003}+1\right)=0\)
\(\Leftrightarrow\dfrac{x+2010}{2005}+\dfrac{x+2010}{2004}+\dfrac{x+2010}{2003}=0\)
`<=>` \(\left(x+2010\right).\left(\dfrac{x}{2005}+\dfrac{x}{2004}+\dfrac{x}{2003}\right)=0\)
Mà : `x/2005 + x/2004 + x/2003` \(\ge0\forall x\) (Loại)`
`=> x + 2010 = 0`
`=> x = 0-2010`
`x=-2010`
