a,
`(x-1)(x+4)=0`
`<=>`\(\left[ \begin{array}{l}x-1=0\\x+4=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=1\\x=-4\end{array} \right.\)
b,
`(2x-4)(x+5)=0`
`<=>`\(\left[ \begin{array}{l}2x-4=0\\x+5=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=2\\x=-5\end{array} \right.\)
c,
`(4x-16)(2x+7)=0`
`<=>`\(\left[ \begin{array}{l}4x-16=0\\2x+7=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=4\\x=-\dfrac{7}{2}\end{array} \right.\)
d,
`(x^2+2)(2x-10)=0`
Vì `x^2+2>0` với mọi `x`
`=>2x-10=0`
`<=>x=5`
e,
`(6x-5)(x^2+7)=0`
Vì `x^2+7>0` với mọi `x`
`=>6x-5=0`
`<=>x=5/6`
f,
`(x^2-1)(x+4)=0`
`<=>(x-1)(x+1)(x+4)=0`
`<=>`\(\left[ \begin{array}{l}x-1=0\\x+1=0\\x+4=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=1\\x=-1\\x=-4\end{array} \right.\)
