a) `x^2+4=4x`
⇔`x^2-4x+4=0`
⇔`(x-2)^2=0`
⇔`x-2=0`
⇔`x=2`
Vậy `S={2}`
b) `4x^2-1=0`
⇔`(2x-1)(2x+1)=0`
⇔\(\left[ \begin{array}{l}2x-1=0\\2x+1=0\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=\dfrac{1}{2}\\x=-\dfrac{1}{2}\end{array} \right.\)
Vậy `S={1/2,-1/2}`
c) `x^3-3x^2+3x=1`
⇔`x^3-3x^2+3x-1=0`
⇔`(x-1)^3=0`
⇔`x-1=0`
⇔`x=1`
Vậy `S={1}`
d) `(x+1)^2-(2x-1)^2=0`
⇔`(x+1-2x+1)(x+1+2x-1)=0`
⇔`(-x+2)3x=0`
⇔\(\left[ \begin{array}{l}-x+2=0\\3x=0\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=2\\x=0\end{array} \right.\)
Vậy `S={2,0}`
