a) 1440 : [ 41 – (2x – 5)] = 16 . 3 b) 5. [225 – ( x- 10 )] – 125 = 0 c) 2 mũ x . 8 = 512 d) ( 2x +

0 bình luận về “a) 1440 : [ 41 – (2x – 5)] = 16 . 3 b) 5. [225 – ( x- 10 )] – 125 = 0 c) 2 mũ x . 8 = 512 d) ( 2x +”

1. a) 1440 : [ 41 – (2x – 5)] = 16.3

   ⇒1440:[41-2x+5]=48

   ⇒46-2x=1440:48

   ⇒46-2x=30

   ⇒2x=46-30

   ⇒2x=16

   ⇒x=8

   b) 5. [225 – ( x- 10 )] – 125 = 0

   ⇒5. [225 – ( x- 10 )]=125

   ⇒225-x+10=125:5

   ⇒235-x=25

   ⇒x=210

   c) $2^x$.8 = 512

   ⇒$2^x=64$

   ⇒$2^x=2^6$

   ⇒x=6

   d) ( 2x + 1)³ = 729

   ⇒(2x+1)³=9³

   ⇒2x+1=9

   ⇒2x=8

   ⇒x=4

   e) |2x + 5| = 1

   ⇒\(\left[ \begin{array}{l}2x+5=1\\2x+5=-1\end{array} \right.\) =>\(\left[ \begin{array}{l}2x=-4\\2x=-6\end{array} \right.\) =>\(\left[ \begin{array}{l}x=-2\\x=-3\end{array} \right.\) 

   Vậy x=-2 hoặc x=-3

   i) 42 – ( 2x + 32) +12 : 2 = -6

   ⇒42-2x-32+6=-6

   ⇒16-2x=-6

   ⇒2x=-8/3

   ⇒x=-4/3

   m) 134 – 2{ 156 – 6.[54-2 .(9+6)]}.x = 86

   ⇒134 – 2{ 156 – 6.[54-2 .15]}.x=86

   ⇒2{ 156 – 6.[54-2 .15]}.x=48

   ⇒{ 156 – 6.[54-2 .15]}.x=24

   ⇒{156-6.24]}.x=24

   ⇒12.x=24

   ⇒x=2

   Bình luận

2. a) $1440 : [41 – (2x – 5)] = 16.3$

   $\Leftrightarrow 1440 : [41 – (2x – 5)] = 48$

   $\Leftrightarrow 41 – (2x – 5) = 30$

   $\Leftrightarrow 41 – 2x + 5 = 30$

   $\Leftrightarrow 46 – 2x = 30$

   $\Leftrightarrow 2x = 46 – 30$

   $\Leftrightarrow 2x = 16$

   $\Leftrightarrow x = 8$

   b) $5.[225 – (x – 10)] – 125 = 0$

   $\Leftrightarrow 5.[225 – (x – 10)] = 125$

   $\Leftrightarrow 225 – (x – 10) = 25$

   $\Leftrightarrow x – 10 = 225 – 25$

   $\Leftrightarrow x – 10 = 200$

   $\Leftrightarrow x = 210$

   c) $2^{x}.8 = 512$

   $\Leftrightarrow 2^{x}.2^{3} = 2^{9}$

   $\Leftrightarrow 2^{x} = 2^{6}$

   $\Leftrightarrow x = 6$

   d) $(2x + 1)^{3} = 729$

   $\Leftrightarrow (2x + 1)^{3} = 9^{3}$

   $\Leftrightarrow 2x + 1 = 9$

   $\Leftrightarrow 2x = 8$

   $\Leftrightarrow x = 4$

   e) $\left | 2x + 5  \right | = 1$

   $\Leftrightarrow \left[ \begin{array}{l}2x+5=1\\2x + 5=-1\end{array} \right.$ $\Leftrightarrow \left[ \begin{array}{l}x=-2\\x=-3\end{array} \right.$

   i) $42 – (2x + 32) + 12 : 2 = -6$

   $\Leftrightarrow 42 – (2x + 32) + 6 = -6$

   $\Leftrightarrow 42 – (2x + 32) = -6 – 6$

   $\Leftrightarrow 42 – (2x + 32) = -12$

   $\Leftrightarrow 2x + 32 = 42 + 12$

   $\Leftrightarrow 2x + 32 = 54$

   $\Leftrightarrow 2x = 22$

   $\Leftrightarrow x = 11$

   m) $134 – 2{156 – 6.[54 – 2.(9+6)]}.x = 86$

   $\Leftrightarrow 2[156 – 6.(54 – 2.15)].x = 134 – 86$

   $\Leftrightarrow 2[156 – 6.(54 – 30)].x = 48$

   $\Leftrightarrow (156 – 6.24).x = 24$

   $\Leftrightarrow (156 – 144).x = 24$

   $\Leftrightarrow 12.x = 24$

   $\Leftrightarrow x = 2$

   Bình luận