~ Bạn tham khảo ~
`(2x-5)^2 = (x-2)^2`
`<=> 4x^2-20x+25=x^2-4x+4`
`<=> 4x^2 - x^2 - 20x + 4x + 25 - 4 =0`
`<=> 3x^2-16x+21=0`
`<=> 3x^2-7x-9x+21=0`
`<=> x(3x-7) - 3(3x-7)=0`
`<=> (x-3)(3x-7)=0`
\(⇔\left[ \begin{array}{l}x-3=0\\3x-7=0\end{array} \right.\)
\(⇔\left[ \begin{array}{l}x=3\\x=\dfrac73\end{array} \right.\)
Vậy `S={3;7/3}`
