\(\left(2x+1\right)^3=343\\ \Rightarrow2x+1=7\\ \Rightarrow x=3\)

(2x+1)³=343

(2x+1)³=7³

2x+1=7

2x=7-1

2x=6

x=6:2

x=3

\(70-5.\left(x-3\right)=45\)

           \(5.\left(x-3\right)=70-45\)

           \(5.\left(x-3\right)=25\)

               \(\left(x-3\right)=25:5\)

               \(\left(x-3\right)=5\)

                             \(x=5+3\)

                             \(x=8.\)

\(\left(2x-1\right)^3=343\)

                \(2x=343+1\)

                \(2x=344\)

                  \(x=344:2\)

                  \(x=172.\)

( Bài này mk cũng ko chắc là lm đúng hay ko, nếu có j sai mong bn thông cảm cho mk )

_Hok tốt_

\(70-5.\left(x-3\right)=45\)

\(5.\left(x-3\right)=70-45\)

\(5.\left(x-3\right)=25\)

\(x-3=25:5\)

\(x-3=5\)

\(x=5+3\)

\(x=8\)

\(\left(2x+1\right)^3=343\)

\(\left(2x+1\right)^3=7^3\)

\(\Rightarrow2x+1=7\)

\(2x=7-1\)

\(2x=6\)

\(x=6:2\)

\(x=3\)

Vậy x = 3

Ta có: (2x + 1)³ = 343

     \(\Leftrightarrow\)(2x + 1)³ = 7³

    \(\Leftrightarrow\)2x + 1 = 7

    \(\Leftrightarrow\)2x = 7 - 1 = 6

    \(\Leftrightarrow\)x = 6: 2 = 3

Vay x = 3

ta có 

(2x+1)^3=343

<=>(2x+1)^3=7^3

=>2x+1=7

=>x=4

\(\left(2x+3\right)^4=625\)

\(\left(2x+3\right)^4=5^4\)

\(\Rightarrow2x+3=5\)

\(2x=5-3\)

\(2x=2\)

\(x=2\div2\)

\(x=1\)

\(\left(3x+1\right)^3=343\)

\(\left(3x+1\right)^3=7^3\)

\(3x+1=7\)

\(3x=7-1\)

\(3x=6\)

\(x=6\div3\)

\(x=2\)

bé nguyên sai rồi câu a ấy . câu đấy có hai trường hợp vì nó mũ chẵn nha bạn

\(\left(2x+3\right)^4=625\)

\(\left(2x+3\right)^4-625=0\)

\(\left(2x+3\right)^4-5^4=0\)

\(\left[\left(2x+3\right)^2-25\right]\left[\left(2x+3\right)^2+25\right]=0\)

Ta có : \(\left(2x+3\right)^2+25>0\)

\(\Rightarrow\left[\left(2x+3\right)^2-25\right]=0\)

\(\Leftrightarrow\left(2x+3-5\right)\left(2x+3+5\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}2x-2=0\\2x+8=0\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=1\\x=-4\end{cases}}\)

\(\left(2x+1\right)^3=343\)

\(\Rightarrow\left(2x+1\right)^3=7^3\)

\(\Rightarrow2x+1=7\)

\(\Rightarrow2x=7-1\)

\(\Rightarrow2x=6\)

\(\Rightarrow x=6:2\)

\(\Rightarrow x=3\)

Vậy x = 3

_Chúc bạn học tốt_

\(\left(2x+1\right)^3=343\)

\(\left(2x+1\right)^3=7^3\)

\(2x+1=7\)

\(2x=7-1\)

\(2x=6\)

\(x=6:2\)

\(x=3\)

Ai đó hãy giúp giải bà này đi 

Chọn A