a) `\sqrt{x^2-2x+1}=2` `(x∈R)`
⇔`\sqrt{(x-1)^2}=2`
⇔`|x-1|=2`
⇔\(\left[ \begin{array}{l}x-1=2\\1-x=2\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=3(tm)\\x=-1(tm)\end{array} \right.\)
Vậy `S={3,-1}`
b) `\sqrt{9x^2-12x+4}=5` `(x∈R)`
⇔`\sqrt{(3x-2)^2}=5`
⇔\(\left[ \begin{array}{l}3x-2=5\\2-3x=5\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=\dfrac{7}{3}(tm)\\x=-1(tm)\end{array} \right.\)
Vậy `S={7/3,-1}`
