`(x-1)^2+x(4-x)=0`
`⇒x^2-2x+1+4x-x^2=0`
`⇒(x^2-x^2)+(-2x+4x)+1=0`
`⇒2x+1=0`
`⇒2x=-1`
`⇒x=-1/2`
Vậy `x=-1/2`
`x(x-2020)+x-2020=0`
`⇒x(x-2020)+(x-2020)=0`
`⇒(x+1)(x-2020)=0`
`⇒` \(\left[ \begin{array}{l}x+1=0\\x-2020=0\end{array} \right.\)
`⇒` \(\left[ \begin{array}{l}x=-1\\x=2020\end{array} \right.\)
Vậy `x∈{-1;2020}`
`(2x-1)^2-(2x+5)(2x-5)-18=0`
`⇒4x^2-4x+1-[(2x)^2-5^2)]-18=0`
`⇒4x^2-4x+1-(4x^2-25)-18=0`
`⇒4x^2-4x+1-4x^2+25-18=0`
`⇒(4x^2-4x^2)-4x+(1+25-18)=0`
`⇒-4x+8=0`
`⇒-4x=-8`
`⇒x=2`
Vậy `x=2`
`5x(x-3)-2x+6=0`
`⇒5x(x-3)-2(x-3)=0`
`⇒(5x-2)(x-3)=0`
`⇒` \(\left[ \begin{array}{l}5x-2=0\\x-3=0\end{array} \right.\)
`⇒` \(\left[ \begin{array}{l}5x=2=>x=2/5\\x=3\end{array} \right.\)
Vậy `x∈{2/5;3}`
