~Gửi bạn~
$\sqrt{4x²-4x+1}=3$
Áp dụng hằng đẳng thức : `(A-B)²=A²-2AB+B²`
`=>` $\sqrt{(2x-1)²}=3$
`=>|2x-1|=3`
`=>` \(\left[ \begin{array}{l}2x-1=(-3)\\2x-1=3\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}2x=(-2)\\2x=4\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}x=(-1)\\x=2\end{array} \right.\)
Vậy `x∈{-1;2}`