`text{Đáp án:}`
`TH1:`
\(\left[ \begin{array}{l}x-3=0\\x=3\end{array} \right.\)
`TH2:`
\(\left[ \begin{array}{l}x-2=0\\x=2\end{array} \right.\)
`text{Giải thích các bước giải:}`
`7x²-35x+42=0`
`⇔7(x²-5x+6)=0`
`⇔x²-5x+6=0`
`⇔(x²-3x)-(2x-6)=0`
`⇔x(x-3)-2(x-3)=0`
`⇔(x-3)(x-2)=0`
Ta có `2TH:`
`TH1:`
\(\left[ \begin{array}{l}x-3=0\\x=3\end{array} \right.\)
`TH2:`
\(\left[ \begin{array}{l}x-2=0\\x=2\end{array} \right.\)