²a) `x³-5x²+x-5=0`
`⇒ (x³-5x²)+(x-5)=0`
`⇒ x²(x-5)+(x-5)=0`
`⇒ (x-5)(x²+1)=0`
`⇒` \(\left[ \begin{array}{l}x-5=0\\x²+1=0\end{array} \right.\)
`⇒` \(\left[ \begin{array}{l}x=5\\x²=-1\end{array} \right.\)
`⇒` \(\left[ \begin{array}{l}x=5\\x=∅\end{array} \right.\)
b) `(x+3)²+(x-2)(x+2)-2(x-1)²=7`
`⇒ x²+6x+9+x²-4-2(x²-2x+1)=7`
`⇒ x²+6x+9+x²-4x-2x²+4x-2=7`
`⇒ 6x+7=7`
`⇒ 6x=0`
`⇒ x=0`
