Đáp án+Giải thích các bước giải:
`x(x-2020)-2x+4040=0`
`<=>x(x-2020)-(2x-4040)=0`
`<=> x(x-2020)-2(x-2020)=0`
`<=> (x-2)(x-2020)=0`
`<=>`\(\left[ \begin{array}{l}x-2=0\\x-2020=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=2\\x=2020\end{array} \right.\)
Vậy `x∈{2; 2020}`