`a, x(x + 3) = 0`
`⇒` \(\left[ \begin{array}{l}x=0\\x+3=0\end{array} \right.\) `⇒` \(\left[ \begin{array}{l}x=0\\x=-3\end{array} \right.\)
`b, (x - 2)(5 - x) = 0`
`⇒` \(\left[ \begin{array}{l}x-2=0\\5-x=0\end{array} \right.\) `⇒` \(\left[ \begin{array}{l}x=2\\x=5\end{array} \right.\)
`c, (x - 1)( x^2 + 1) = 0`
`⇒` \(\left[ \begin{array}{l}x-1=0\\x^2+1=0\end{array} \right.\) `⇒` \(\left[ \begin{array}{l}x=1\\x^2=-1⇒x∈∅\end{array} \right.\)
`d, -12(x - 5) + 7(3 - x) = 5`
`⇒ -12x + 60 + 21 - 7x = 5`
`⇒ -19x = -76`
`⇒ x = -4`
`e, 30(x + 2) - 6(x - 5) - 24x = 100`
`⇒ 30x + 60 - 6x + 30 - 24x = 100`
`⇒ 0 = 10` $\text{(vô lí)}$
`⇒ x ∈ ∅`
`f, |2x - 5| = 13`
`⇒` \(\left[ \begin{array}{l}2x-5=13\\2x-5=-13\end{array} \right.\) `⇒` \(\left[ \begin{array}{l}x=9\\x=-4\end{array} \right.\)
`g, |7x + 3| = 66`
`⇒` \(\left[ \begin{array}{l}7x+3=66\\7x+3=-66\end{array} \right.\) `⇒` \(\left[ \begin{array}{l}x=9\\x=\dfrac{-69}{7}\end{array} \right.\)
`h, |5x - 2| = 0`
`⇒ 5x - 2 = 0`
`⇒ 5x = 2`
`⇒ x = 2/5`