Đáp án + Giải thích các bước giải:
`2(x-3)+x^2-3x=0`
`<=>2x - 6 +x^2 - 3x = 0`
`<=>x^2 - x - 6=0`
`<=> x^2 +2x - 3x-6=0`
`<=> (x^2+2x)-(3x+6)=0`
`<=>x(x+2)-3(x+2)=0`
`<=> (x-3)(x+2)=0`
`<=>` \(\left[ \begin{array}{l}x-3=0\\x+2=0\end{array} \right.\)
`<=>` \(\left[ \begin{array}{l}x=3\\x=-2\end{array} \right.\)
Vậy `x∈{-2;3}`
`b, x^2 - 4x + 4 =9`
`<=> (x-2)^2 - 3^2=0`
`<=> (x-2-3)(x-2+3)=0`
`<=> (x-5)(x+1)=0`
`<=>` \(\left[ \begin{array}{l}x-5=0\\x+1=0\end{array} \right.\)
`<=>` \(\left[ \begin{array}{l}x=5\\x=-1\end{array} \right.\)
Vậy `x∈{5;-1}`
