Câu `1:`
`(x+3)(x-7)=0`
`⇒`\(\left[ \begin{array}{l}x+3=0\\x-7=0\end{array} \right.\)
`⇒`\(\left[ \begin{array}{l}x=-3\\x=7\end{array} \right.\)
`⇒`Chọn `B`
Câu `2:`
`3x(x-7)+5(x-7)=0`
`⇒(3x+5)(x-7)=0`
`⇒`\(\left[ \begin{array}{l}x-7=0\\3x+5=0\end{array} \right.\)
`⇒`\(\left[ \begin{array}{l}x=7\\x=\dfrac{-5}{3} \end{array} \right.\)
`⇒`Chọn `B`
Câu` 3:`
$x^{2}$ `-1=0`
`⇒(x-1)(x+1)=0`
`⇒`\(\left[ \begin{array}{l}x+1=0\\x-1=0\end{array} \right.\)
`⇒`\(\left[ \begin{array}{l}x=-1\\x=1\end{array} \right.\)
`⇒`Chọn `B`