`1.`
`a)6x^2(3x^2-4x+5)`
`=18x^5-24x^3+30x^2`
`b)(x-2y)(3xy+6y^2+x)`
`=3x^2y+6xy^2+x^2-6xy^2-12y^3-2xy`
`=3x^2y+x^2-12y^2-2xy`
`c)(18x^4y^3-24x^3y^4+12x^3y^3):(-6x^2y^3)`
`=-3x^2+4xy-2x`
`3.`
`a)5x(x-2)+3x-6=0`
`⇒5x(x-2)+3(x-2)=0`
`⇒(5x+3)(x-2)=0`
`⇒` \(\left[ \begin{array}{l}5x+3=0\\x-2=0\end{array} \right.\)
`⇒` \(\left[ \begin{array}{l}5x=-3=>x=-3/5\\x=2\end{array} \right.\)
Vậy `x∈{-3/5;2}`
`b)x^3-9x=0`
`⇒x(x^2-9)=0`
`⇒x(x^2-3^2)=0`
`⇒x(x-3)(x+3)=0`
`⇒x=0;x-3=0;x+3=0`
`⇒x=0;x=3;x=-3`
Vậy `x∈{0;±3}`
`c)3x^3-3x=0`
`⇒3x(x^2-1)=0`
`⇒` \(\left[ \begin{array}{l}3x=0\\x^2-1=0\end{array} \right.\)
`⇒` \(\left[ \begin{array}{l}x=0\\x=±1\end{array} \right.\)
Vậy `x∈{0;±1}`
`d)x(x-2)+x-2=0`
`⇒x(x-2)+(x-2)=0`
`⇒(x+1)(x-2)=0`
`⇒` \(\left[ \begin{array}{l}x+1=0\\x-2=0\end{array} \right.\)
`⇒` \(\left[ \begin{array}{l}x=-1\\x=2\end{array} \right.\)
Vậy `x∈{-1;2}`
