a) 5^x = 125

   5³ = 125

Vậy x = 3

b) 3^x = 81

   3⁴ = 81

Vậy x = 4

c)5^2x-3 - 2 . 5² = 5² . 3

5^{2x-3 =} 5² . 3 + 2. 5²

5^2x-3 = 5² . ( 3 + 2 )

5^2x-3 = 5² . 5

5^2x-3 = 5³

=> 2x - 3 = 3

     2x = 6

     x = 3

Vậy x = 3

a) 5^x = 125

\(\Rightarrow\)5^x = 5³

\(\Rightarrow\)x = 3

b, 3^2x = 81

\(\Rightarrow\)3^2x = 3⁴

\(\Rightarrow\)2x = 4

\(\Rightarrow\)  x = 4 : 2

\(\Rightarrow\)  x = 2

c, 5^2x-3 - 2 . 5² = 5² . 3

5^2x-3 - 2 . 25 = 25 . 3

5^2x-3 - 50 = 75

5^2x-3 = 75 + 50

5^2x-3 = 125

5^2x-3 = 5³

2x - 3 = 3

2x = 3 + 3

2x = 6

  x = 6 : 2

  x = 3

a, 5^x = 125 suy ra 5^x = 5³ suy ra x = 3

b, 3^2x = 81 suy ra 3^2x = 3⁴ suy ra x = 2

c, 5^{2x - 3} - 2.5² = 5² . 3

suy ra 5^2x : 5³ = 5² .3 + 2. 5²

suy ra 5^2x : 5³ = 5² . 5

suy ra 5^2x = 5³ . 5² . 5³

5^2x = 5⁶ suy ra 2x = 6 suy ra x = 3

a) \(5^x\)= 125

\(\Leftrightarrow\)\(5^x\)= \(5^3\)\(\Rightarrow\)x = 3

b) \(3^{2x}\)= 81 

\(\Leftrightarrow\)\(3^{2x}\)= \(3^4\)\(\Rightarrow\)\(2\)x = \(4\) \(\Rightarrow\)x = \(\frac{4}{2}\)= \(2\)

c) \(5^{2x-3}\)- \(2\) . \(5^2\)= \(5^2\). \(3\)

\(\Rightarrow\)\(5^{2x}\): \(5^3\)- \(2\) . \(5^2\)= \(5^2\). \(3\)

\(\Rightarrow\)\(5^{2x}\): \(5^3\)= \(5^2\). \(3\) + \(5^2\). \(2\)

\(\Rightarrow\)\(5^{2x}\): \(5^3\)= \(5^2\). \(\left(3+2\right)\)

\(\Rightarrow\)\(5^{2x}\): \(5^3\)= \(5^2\). \(5\)= \(5^3\)

\(\Rightarrow\)\(5^{2x}\)= \(5^3\). \(5^3\)= \(5^6\)

\(\Rightarrow\)\(2x\)= \(6\)

\(\Rightarrow\)\(x\)= \(\frac{6}{2}\)= \(3\)

a,5^x=125

=>5^x=5^3

=>x=3

b,3^2x=81

=>3^2x=3^4

=>2x=4

=>x=4:2=2

c,5^2x-3-2*5^2=5^2+3

5^2x-3-50=75

5^2x-3=75+50=125

5^2x-3=5^3

=>2x-3=3

=>2x=3+3=6

=>6:2=3

k cho mk nhé

\(a,125=5\cdot5\cdot5=5^3\Leftrightarrow x=3\)

\(b,81=3\cdot3\cdot3\cdot3=3^4\Leftrightarrow2x=4\Leftrightarrow x=4:2\Leftrightarrow x=2\)

\(c,5^{2x-3}-2\cdot5^2=5^2\cdot3\)

\(\Leftrightarrow5^{2x-3}=2\cdot5^2+5^2\cdot3\)

\(\Leftrightarrow5^{2x-3}=5^2\cdot\left(2+3\right)\)

\(\Leftrightarrow5^{2x-3}=5^2\cdot5\Leftrightarrow5^{2x-3}=5^3\)

\(\Leftrightarrow2x-3=3\Leftrightarrow2x=3+3\Leftrightarrow2x=6\Leftrightarrow x=6:2\Leftrightarrow x=3\)

a.Ta thấy :\(125=5^3\)\(\Rightarrow x=3\)

b.Ta thấy : \(81=3^4\)\(\Rightarrow2x=4\Rightarrow x=2\)

c.Ta có:

\(5^{2x-3}-2.5^2=5^2.3\)

\(5^{2x-3}=5^2.3+5^2.2\)

\(5^{2x-3}=5^2.5\)

\(5^{2x-3}=5^3\)

\(\Rightarrow2x-3=3\)

     \(2x=3+3\)

     \(2x=6\)

     \(\Rightarrow x=3\)    

a)5^x=125=5³

=>x=3

b)3^2x=81=3⁴

=>2x=4

x=4/2

x=2

c)5^2x-3-2*5²=5²*3

5^2x-3=5²*3+2*5²=5²(3+2)=5²*5

5^2x-3=5³

=>2x-3=3

2x=3+3

2x=6

x=6/2

x=3

lần sau nếu ghi dẫu mũ như vậy thì bạn nhớ ngoặc vào 

chịu mới lớp 4 mà !!!

hỏi làm chi

ai hoi may 

a) x = 3 .                              

a) 5^x = 125

5^x = 5³

=> x = 3

b)  ( mình bó tay )

c) 5^2x-3 -  2.5² = 5² .3

5^2x-3 - 50 = 75

5^2x-3  = 75 + 50

5^2x-3  = 125

5^2x-3  = 5³

2x-3 = 3

2x = 3+3

2x = 6

x = 6 : 2

x = 3

ai trả lời nhanh mk k cho

a, x = 3

b, x ko có giá trị để 32^x = 81

c,  5^2x-3- 50 =75

    5^2x-3       = 75 + 50

    5^2x-3        = 125   \(\Rightarrow\)x = 8

a)x=3

b) ko có x thỏa mãn vì 32^x là chẵn còn 81 là lẻ

c)5^2x-3-2.5²=5².3

5^2x-3=5².3+2.5²

5^2x-3=5²(3+2)

5^2x-3=5².5

5^2x-3=5³

=>2x-3=3

2x=3+3

2x=6

x=6:2

x=3

a,Vì |a|<5

=>|a|\(\in\){0,1,2,3,4}

=>a\(\in\){-4,-3,-2,-1,0,1,2,3,4}

=>-5<a<5\(\left(đpcm\right)\)

b,5^x=125

=>5^x=5³

=>x=3

c,3^2x=81

=>(3²)^x=81

=>9^x=81

=>9^x=9²

=>x=2

d,5^2x-3-2.5²=5².3

=>5^2x:5³-2.25=25.3

=>5^2x:5³-50=75

=>5^2x:5³=75+50

=>5^2x:5³=125

=>5^2x=125.5³

=>5^2x=5³.5³

=>5^2x=5⁶

=>2x=6

=>x=3

a) x= 3

b) x= 2

a/ x= 3

b /x= 2

c /x = 3

olm duyệt đi

5^x=125

=>5^xx=5³

=> x=3

Vậy x=3

3^2x=81

=>3^2x=3⁴

=>2x=4

=>x=4:2=2

Vậy x=2

Tk mk

a, => 5^x = 5^3

=> x = 3

b, => 3^2x = 3^4

=> 2x = 4

=> x = 2

Tk mk nha

a,5^x=125

5^x=5³

=>x=3

b,3^2x=81

3^2x  = 3⁴

=>. 2x = 4

=> x = 4 : 2

=> x = 2

~~ học tốt ~~

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