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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 6: Tìm số nguyên x, biết: a, 14-(x-2)^2=5 b, (72-x)+6^15:6^14=21 c, 3^x+1+3^x+2=324

Toán Lớp 6: Tìm số nguyên x, biết:
a, 14-(x-2)^2=5
b, (72-x)+6^15:6^14=21
c, 3^x+1+3^x+2=324

Comments ( 2 )

  1. $ a) 14 – ( x-2)^2 = 5 $
    $ (x-2)^2 = 14-5=9 $ 
    $ ⇒ $ \(\left[ \begin{array}{l}x-2=3\\x-2=-3\end{array} \right.\) 
    $ ⇒ $ \(\left[ \begin{array}{l}x=5\\x=-1\end{array} \right.\) 
    $ b) ( 72-x) + 6^{15} : 6^{14} = 21 $ 
    $ ( 72-x) + 6 = 21 $ 
    $ 72-x = 21-6=15 $ 
    $ x = 72 – 15=57 $ 
    $c) 3^{x+1} + 3^{x+2} = 324 $ 
    $  3^x . 3 + 3^x . 9 = 324 $
    $ 3^x . ( 3+9) = 324 $ 
    $ 3^x . 12 = 324 $ 
    $ 3^x=324:12=27⇒x=3$

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222-9+11+12:2*14+14 = ? ( )