Toán Lớp 6: a/ 89 – (73 – x) = 20 b/ x – 36 : 18 = 12 + 15 c/ 16. 4^x = 4⁸ d/ 8.x + 20 = 76

TRẢ LỜI

1. $\text{a/ 89 – (73 – x) = 20}$ $\\$ $\text{73 – x = 89 – 20}$ $\\$ $\text{73 – x = 69}$ $\\$ $\text{x = 73 – 69}$ $\\$ $\text{x = 4}$ $\\$ $\text{b/ x – 36 : 18 = 12 + 15 }$ $\\$ $\text{x – 2 = 27}$ $\\$ $\text{x = 27 + 2}$ $\\$ $\text{x = 29}$ $\\$ $\text{c/ 16. $4^{x}$ = $4^{8}$}$ $\\$ $\text{$4^{2}$ $4^{x}$ = $4^{8}$}$ $\\$ $\text{$4^{2 + x}$ = $4^{8}$}$ $\\$ $\text{2 + x = 8}$ $\\$ $\text{x = 8 – 2}$ $\\$ $\text{x = 6}$ $\\$ $\text{d/ 8.x + 20 = 76}$ $\\$ $\text{8x = 76 – 20}$ $\\$ $\text{8x = 56}$ $\\$ $\text{x = 56 : 8}$ $\\$ $\text{x = 7}$

    

   Trả lời
2. $ a) 89 – ( 73 – x ) = 20 $

   $ 73 – x = 89 – 20 = 69 $

   $ x = 73 – 69 = 4 $

   $ b) x – 36 : 18 = 12 + 15 = 27 $

   $ x – 2 = 27 $

   $ x = 27 + 2 = 29 $ 

   $ c) 16 . 4^x = 4^8 $

   $ 4^2 . 4^x = 4^8 $

   $ 4^{2+x} = 4^8 $

   $ ⇒ 2 + x = 8 $

   $ x = 8 – 2 = 6 $

   $ d) 8x + 20 = 76 $

   $ 8x = 76 – 20 = 56 $

   $ x = 56 : 8 = 7 $ 

   Trả lời