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Bài 6A:
`a)x(x-6)=0`
`⇒`\(\left[ \begin{array}{l}x=0\\x-6=0\end{array} \right.\)
`⇒`\(\left[ \begin{array}{l}x=0\\x=6\end{array} \right.\)
`b)x(x+5)=0`
`⇒`\(\left[ \begin{array}{l}x=0\\x+5=0\end{array} \right.\)
`⇒`\(\left[ \begin{array}{l}x=0\\x=-5\end{array} \right.\)
`c)(x+3)(x-7)=0`
`⇒`\(\left[ \begin{array}{l}x+3=0\\x-7=0\end{array} \right.\)
`⇒`\(\left[ \begin{array}{l}x=-3\\x=7\end{array} \right.\)
`d)(x-3)(x^2+12)=0`
Có `x^2≥0 ∀x⇒x^2+12>0`
`⇒x-3=0`
`⇒x=3`
Câu 6B:
`a)x(x-1)=0`
`⇒`\(\left[ \begin{array}{l}x=0\\x-1=0\end{array} \right.\)
`⇒`\(\left[ \begin{array}{l}x=0\\x=1\end{array} \right.\)
`b)x(x+1)=0`
`⇒`\(\left[ \begin{array}{l}x=0\\x+1=0\end{array} \right.\)
`⇒`\(\left[ \begin{array}{l}x=0\\x=-1\end{array} \right.\)
`c)(x+1)(x-3)=0`
`⇒`\(\left[ \begin{array}{l}x+1=0\\x-3=0\end{array} \right.\)
`⇒`\(\left[ \begin{array}{l}x=-1\\x=3\end{array} \right.\)
`d)(x-1)(x^2+1)=0`
Có `x^2≥0 ∀x⇒x^2+1>0`
`⇒x-1=0`
`⇒x=1`
