Bài 3:

`(2x-1)^8=(2x-1)^6`

`⇔(2x-1) ∈ {-1; 0; 1}`

`⇒+) 2x-1=1`

`2x=1+1`

`2x=2`

`x=2:2`

`x=1`

`+)2x-1=-1`

`2x=-1+1`

`2x=0`

`x=0:2`

`x=0`

`+)2x-1=0`

`2x=0+1`

`2x=1`

`x=1:2`

`x=1/2`

`\text{Vậy}` `x=1; x=0; x=1/2`

Bài 4:

`1) 3^x+3^(x+2)=2430`

`3^x .1+3^x .3^2=2430`

`3^x .(1+3^2)=2430`

`3^x .(1+9)=2430`

`3^x .10=2430`

`3^x=2430:10`

`3^x=243`

`3^x=3^5`

`⇒x=5`

`\text{Vậy x=5}`

`2) 3^(x-1)+5.3^(x-1)=162`

`3^(x-1).(1+5)=162`

`3^(x-1).6=162`

`3^(x-1)=162:6`

`3^(x-1)=27`

`3^(x-1)=3^3`

`⇒x-1=3`

`x=3+1`

`x=4`

`\text{Vậy x=4}`

(Cho mình xin câu trả lời hay nhất nha 🥰🥰🥰 )

Chúc bạn học tốt~~~

`@Nhi`

$\text{Bài 3 :}$

`(2x-1)^8=(2x-1)^6`

`⇒(2x-1)^8-(2x-1)^6=0`

`⇒(2x-1)^6 . [(2x-1)²-1]=0`

`⇒`\(\left[ \begin{array}{l}(2x-1)^6=0\\(2x-1)²-1=0\end{array} \right.\) 

$\text{TH1 :}$ `(2x-1)^6=0`

    `⇒ 2x-1=0`

    `⇒ 2x=1`

     `⇒ x=1/2`

$\text{TH2 :(2x-1)²-1=0 }$

     `⇒ (2x-1)²=1`

     `⇒`\(\left[ \begin{array}{l}2x-1=1\\2x-1=-1\end{array} \right.\) 

     `⇒`\(\left[ \begin{array}{l}2x=2\\2x=0\end{array} \right.\) 

     `⇒`\(\left[ \begin{array}{l}x=1\\x=0\end{array} \right.\) 

$\text{Bài 4 :}$

`a)` `3^x + 3^(x+2)=2430`

  `⇒ 3^x.(1+3²)=2430`

  `⇒ 3^x .10=2430`

  `⇒ 3^x=243`

  `⇒ 3^x = 3^5`

   `⇒ x=5`

`b)` `3^(x-1) +5.3^(x-1)=162`

    `⇒ 3^(x-1) .(1+5)=162`

    `⇒ 3^(x-1) . 6=162`

     `⇒ 3^(x-1)= 27`

      `⇒3^(x-1)=3³`

      `⇒ x-1=3`

      `⇒ x=4`