Question

2(3x-1)\(^2\)-1=7

Answer 1

\(2\left(3x-1\right)^2-1=7\\ \Leftrightarrow2\left(3x-1\right)^2=8\\ \Leftrightarrow\left(3x-1\right)^2=\dfrac{8}{2}=4\\ \Leftrightarrow\left[{}\begin{matrix}3x-1=2\\3x-1=-2\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}3x=3\\3x=-1\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=1\\x=-\dfrac{1}{3}\end{matrix}\right.\)

Vậy ...... 

Answer 2

=>2(3x-1)^2=8

=>(3x-1)^2=4

=>3x-1=2 hoặc 3x-1=-2

=>3x=-1 hoặc 3x=3

=>x=1 hoặc x=-1/3