Cho a,b € Z. Tìm x€ Z sao cho: a, x – a = 2 b, x + b = 4 c, a – x = 21 d, 14 – x = b + 9

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1. $\text{Cho a,b € Z. Tìm x€ Z sao cho :}$

   $\text{a, x – a = 2}$

   `->` $\text{x = 2 + a}$

   $\text{b, x + b = 4}$

   `->` $\text{x = 4 – b}$

   $\text{c, a – x = 21}$

   `->` $\text{x = a – 21}$

   $\text{d, 14 – x = b + 9}$

   `->` $\text{x = 14 – ( b + 9 )}$

   `->` $\text{x = 14 – b – 9}$

   `->` $\text{x = 5 – b}$

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2. a, x – a = 2

   ⇒ x = 2 + a

   b, x + b = 4 

   ⇒ x = 4 – b

   c, a – x = 21

   ⇒ x = a – 21

   d, 14 – x = b + 9

   ⇒ x = 14 – ( b + 9 )

        x = 14 – b – 9 = 5 – b

   $@yenngoc$

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