b. (x - 1).(x+5)
<=> \(\left[{}\begin{matrix}x-1=0\\x+5=0\end{matrix}\right.\)
<=>\(\left[{}\begin{matrix}x=1\\x=-5\end{matrix}\right.\)
d, x\(^2\)+4x <=> x(x+4) <=>\(\left[{}\begin{matrix}x=0\\x=-4\end{matrix}\right.\)
`a. 5x - 1/3=0`
`<=>5x=1/3`
`<=>x=1/3 :5`
`<=>x=1/15`
`b. (x - 1).(x+5)=0`
\(\Leftrightarrow\left[{}\begin{matrix}x-1=0\\x+5=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-5\end{matrix}\right.\)
`c. (x+1).(x²+2)=0`
\(\Leftrightarrow\left[{}\begin{matrix}x+1=0\\x^2+2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-2\left(vôlí\right)\end{matrix}\right.\)
`d. x²+4x=0 `
`<=>x(x+4)=0`
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x+4=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-4\end{matrix}\right.\)
`e. x² - 7x+6=0 `
`<=> x^2 -1x -6x+6=0`
`<=>x(x-1)-6(x-1)=0`
`<=>(x-6)(x-1)=0`
\(\Leftrightarrow\left[{}\begin{matrix}x-6=0\\x-1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=6\\x=1\end{matrix}\right.\)
`g. 2x² - 3x + 1=0`
`<=>2x^2 -2x -1x +1=0`
`<=>2x(x-1)-1(x-1)=0`
`<=>(2x-1)(x-1)=0`
\(\Leftrightarrow\left[{}\begin{matrix}2x-1=0\\x-1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{2}\\x=1\end{matrix}\right.\)
