`1.` `A` vì `x=-20`
`2.` `C` cùng tập nghiệm `S={-4;4}`
`3.` `<=>` \(\left[ \begin{array}{l}x-3=0\\x^3-x^2=0\end{array} \right.\)
`<=>` $\left[\begin{array}{ccc}x=3\\x=0\\x=1\end{array}\right.$
`->` `D`
`4.` Ta có: `x-6=0` `x=6`
`=>` `x` $\neq$ `6`
`->` `A`
`5`. \(\left[ \begin{array}{l}x-1=0\\x+2=0\end{array} \right.\) `<=>` \(\left[ \begin{array}{l}x=1\\x=-2\end{array} \right.\)
`=>` `x` $\neq$ `1`, `x` $\neq$ `-2`
`->` `C`
`6`. ĐKXĐ: `x` $\neq$ `-2;0`
`=>` `-3x=5(x-2)
`<=>` `-3x=5x+10`
`<=>` `-3x-5x=10`
`<=>` `-8x=10`
`<=>` `x=-5/4` (t.m)
`->` `C`
