giúp e bài 8 ạ thanks trc

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1. a)$2^{n}$=16

   $2^{n}$=$2^{4}$ 

   ⇒n=4

   Vậy n=4

   b)$3^{n}$=27

   $3^{n}$=$3^{3}$ 

   ⇒n=3

   Vậy n=3

   c)$5^{n}$=625

   $5^{n}$=$5^{4}$ 

   ⇒n=4

   Vậy n=4

   d)$12^{n}$=144

   $12^{n}$=$12^{2}$ 

   ⇒n=2

   Vậy n=2

   e)$3^{n}$÷9=27

   $3^{n}$       =27.9

   $3^{n}$       =243

   $3^{n}$       =$3^{5}$

   ⇒n=5

   Vậy n=5

   f)$2^{n}$×16       =128

   $2^{n}$×$2^{4}$ =$2^{7}$

   $2^{n}$                =$2^{7}$÷$2^{4}$ 

   $2^{n}$                =$2^{3}$

   ⇒n=3

   Vậy n=3

   g)$2^{n}$-15=17

   $2^{n}$        =17-15

   $2^{n}$        =2

   $2^{n}$        =$2^{1}$

   ⇒n=1

   Vậy n=1

   h)2.$3^{n}$=10.$3^{12}$+8.$27^{4}$

   10.$3^{12}$+8.$27^{4}$=2.$3^{n}$

   10.$3^{12}$+8.[($3^{{3})4}$]=2.$3^{n}$ 

   10.$3^{12}$+8.$3^{12}$=2.$3^{n}$   

   $3^{12}$.(8+10)=2.$3^{n}$  

   $3^{12}$÷$3^{n}$.18=2

   $3^{12}$÷$3^{n}$.2³=2

   $3^{12-x}$÷$3^{2}$.2=2

   $3^{12-x+2}$=2÷2

   $3^{14-x}$=1

   ⇒14-x=0

   x=14-0

   x=14

   Vậy x=14

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2. @Bơ

   `2^{n}=16`

   `=>2^{n}=2^4`

   `n=4`

   `3^{n}=27`

   `=>3^{n}=3^3`

   `n=3`

   `5^{n}=625`

   `=>5^{n}=5^4`

   `n=4`

   `12^{n}=144`

   `=12^{n}=12^2`

   `n=2`

   `3^{n}:9=27`

   `3^{n}=27.9`

   `3^{n}=243`

   `=>3^{n}=3^5`

   `n=5`

   `2^{n }.  16=128`

   `2^{n}=128:16`

   `2^{n}=8`

   `=>2^{n}=2^3`

   `n=3`

   `2^{n}-15=17`

   `2^{n}=17-15`

   `2^{n}=2`

   `=>2^{n}=2^1`

   `n=1`

   `2.3^{n}=10.3^{12}+8.27^{4}`

   `2.3^{n}=10.3^{12}+8}.3{12}`

   `2.3^{n}=(10+8).(3^{12}.3^{12})`

   `2.3^{n}=18.3^24`

   `2.3^{n}=2.3^{2}.3^{24}`

   `2.3^{n}=2.3^{26}`

   `=>3^{n}=3^{26}`

   `n=26`

    

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