`C1` `\frac{x-3}{4}` = `\frac{2-x}{-7}` `C2` `\frac{2x-1}{-3}` = `\frac{4-5x}{-7}` `C3` `\frac{x+8}{-21}` = `\frac{-3x+2}{13}`

0 bình luận về “`C1` `\frac{x-3}{4}` = `\frac{2-x}{-7}` `C2` `\frac{2x-1}{-3}` = `\frac{4-5x}{-7}` `C3` `\frac{x+8}{-21}` = `\frac{-3x+2}{13}`”

1. Đáp án:

    $C1 \dfrac{x-3}{4}=\dfrac{2-x}{-7}$

   $⇔\dfrac{-7(x-3)}{-28} = \dfrac{4(2-x)}{-28}$

   $⇔-7(x-3) = 4(2-x)$

   $⇔-7x+21 = 8 -4x$

   $⇔-7x+4x=8-21$

   $⇔-3x =-13$

   $⇔x=-13 : (-3)$

   $⇔x = \dfrac{13}{3}$

   Vậy $x=\dfrac{13}{3}$

   $C2 \dfrac{2x-1}{-3} = \dfrac{4-5x}{-7}$

   $⇔\dfrac{-7(2x-1)}{21} = \dfrac{-3(4-5x)}{21}$

   $⇔-7(2x-1) = -3(4-5x)$

   $⇔-14x +7 = -12 +15x$

   $⇔-14x-15x=-12-7$

   $⇔-29x = -19$

   $⇔x = -19 : (-29)$

   $⇔x=\dfrac{19}{29}$

   Vậy $x=\dfrac{19}{29}$

   $C3 \dfrac{x+8}{-21} =\dfrac{-3x+2}{13}$

   $⇔\dfrac{13(x+8)}{-273} =\dfrac{-21(-3x+2)}{-273}$

   $⇔ 13(x+8) = -21(-3x+2)$

   $⇔13x+104=63x -42$

   $⇔ 13x-63x = -42 -104$

   $⇔-50x =-146$

   $⇔x = -146 : (-50)$

   $⇔x=\dfrac{73}{25}$

   Vậy $x=\dfrac{73}{25}$

    

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2. Đáp án:

    C1: x-3/4=2-x/-7

   ⇒-7x+21=8-4x

   ⇒  21-8  =-4x+7x

   ⇒    13   =3x

   ⇒   x      =13/3

   Vậy x=13/3

   C2: 2x-1/-3=4-5x/-7

   ⇒-14x+7   =-12+15x

   ⇒     7+12 =15x+14x

   ⇒      19    =29x

   ⇒       x     =19/29

    Vậy x=19/29

   C3: x+8/-21=-3x+2/13

   ⇒  13x+104=63x-42

   ⇒   104+42=63x-13x

   ⇒     146     =50x

   ⇒          x    =2,92

    Vậy x=2,92

    

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