Question

a, |3x -1| - 5 = 2          b, 9 ngu x :  3 ngu x = 81 

Tim x  

Answer 1

\(a,\Leftrightarrow\left|3x-1\right|=7\Leftrightarrow\left[{}\begin{matrix}3x-1=7\\1-3x=7\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{8}{3}\\x=-2\end{matrix}\right.\\ b,\Leftrightarrow3^{2x}:3^x=81=3^4\\ \Leftrightarrow3^x=3^4\Leftrightarrow x=4\)

Answer 2

a: \(\Leftrightarrow\left|3x-1\right|=7\)

\(\Leftrightarrow\left[{}\begin{matrix}3x-1=7\\3x-1=-7\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{8}{3}\\x=-2\end{matrix}\right.\)

Answer 3

a) |3x - 1| -5=2

|3x - 1| =2+5

|3x - 1|=7

⇒3x - 1 =7 hoặc 3x - 1= -7

TH1:

3x-1=7

3x=7+1

3x=8

x=8:3

x=\(\dfrac{8}{3}\)

TH2:

3x - 1 = -7

3x= -7+1

3x= -6

x= (-6):3

x=-2

Vậy x∈{\(\dfrac{8}{3}\);-2}

b) 9\(^x\):3\(^x\)=81

(9:3)\(^x\)=81

3\(^x\)=81

3\(^x\)=3\(^4\)

⇒x=4

Vậy x=4