8.(12+35)-12.(8-35) |x-2|=5 2-7.x=-47 |4.x-12|=8

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1. a, 8.(12+35)-12.(8-35)

   = 8.12 + 8.35 – 12.8 + 12.35

   = 8.35 + 12.35

   = 35.(8+12)

   = 35.20

   = 700

   b, |x-2|=5

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

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

   Vậy x ∈ {-3;7}

   c, 2-7.x=-47

   => 7x = 2 – (-47)

   => 7x = 49

   => x = 7 

   Vậy x = 7

   d, |4x-12|=8

   => \(\left[ \begin{array}{l}4x-12=8\\4x-12=-8\end{array} \right.\) 

   => \(\left[ \begin{array}{l}4x=20\\4x=4\end{array} \right.\)

   => \(\left[ \begin{array}{l}x=5\\x=1\end{array} \right.\)

   Vậy x ∈ {1;5}

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2. Giải

   a,8.(12+35)-12.(8-35)=8.47-12.(-27)=376-(-324)=376+324=700

   b,║x-2║=5

   ⇒ \(\left[ \begin{array}{l}x-2=5 => x=5+2=7\\x-2=-5=> x=-5+2=-3\end{array} \right.\) 

   c,2-7.x=-47

         7x=2-(-47)=49

          x=49:7=7

   d, ║4.x-12║=8║

   ⇒ \(\left[ \begin{array}{l}4x-12=8=>4x=8+12=20=>x=20:4=5\\4x-12=-8=>4x=-8+12=4=>x=4:4=1\end{array} \right.\)                                      

                                                                 

      

    

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