`a)x^2+5x=0`
`⇒x(x+5)=0`
`⇒` \(\left[ \begin{array}{l}x=0\\x+5=0=>x=-5\end{array} \right.\)
Vậy `x∈{0;-5}`
`b)x^2+4x=0`
`⇒x(x+4)=0`
`⇒` \(\left[ \begin{array}{l}x=0\\x+4=0=>x=-4\end{array} \right.\)
Vậy `x∈{0;-4}`
`c)x^2+2x=0`
`⇒x(x+2)=0`
`⇒` \(\left[ \begin{array}{l}x=0\\x+2=0=>x=-2\end{array} \right.\)
Vậy `x∈{0;-2}`
`d)x^2+6x=0`
`⇒x(x+6)=0`
`⇒` \(\left[ \begin{array}{l}x=0\\x+6=0=>x=-6\end{array} \right.\)
Vậy `x∈{0;-6}`
