1 tìm x biết a, 3/4+x=-1/6 b, x-7/9=11/3 c, x+1/2=8/x+1 d,/2x-3/=7

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1. Đáp án:

    

   Giải thích các bước giải:

    a)

   $\dfrac{3}{4} + x = \dfrac{-1}{6}$

   $x = \dfrac{-1}{6} – \dfrac{3}{4} $

   $x = \dfrac{-11}{12}$

   b)

   $x – \dfrac{7}{9}  = \dfrac{11}{3} $

   $x = \dfrac{11}{3} + \dfrac{7}{9}$

   $x = \dfrac{40}{9}$

   c)

   \dfrac{x+1}{2} = \dfrac{8}{x+1}

   (x+1)² = 2 . 8

   (x+1)² = 16

   ⇒ x+1 = ±4

   \(\left[ \begin{array}{l}x=3\\x=-5\end{array} \right.\) 

   d)

   $| 2x – 3 | = 7$

   $2x – 3 = ±7$

   \(\left[ \begin{array}{l}2x – 3=7\\2x – 3=-7\end{array} \right.\) 

   \(\left[ \begin{array}{l}2x=10\\2x=-4\end{array} \right.\) 

   \(\left[ \begin{array}{l}x=5\\x=-2\end{array} \right.\) 

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2. a) `3/4+x=-1/6`

   `→x=-1/6-3/4`

   `→x=-(11)/(12)`

   b) `x-7/9=11/3`

   `→x=11/3+7/9`

   `→x=40/9`

   c) `(x+1)/2=8/(x+1)`

   `→(x+1)(x+1)=2.8`

   `→(x+1)²=16`

   \(→\left[ {\matrix{{x+1=4} \cr{x+1=-4} \cr} } \right.\)

   \(→\left[ {\matrix{{x=3} \cr{x=-5} \cr} } \right.\)

   d) `|2x-3|=7`

   \(→\left[ {\matrix{{2x-3=7} \cr{2x-3=-7} \cr} } \right.\)

   \(→\left[ {\matrix{{2x=10} \cr{2x=-4} \cr} } \right.\)

   \(→\left[ {\matrix{{x=5} \cr{x=-2} \cr} } \right.\)

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