a)
`7x + 49 = 0`
` => 7x = -49`
` => x = -7`
b)
` 23x(x-2) = 0`
=> \(\left[ \begin{array}{l}23x= 0\\x-2=0\end{array} \right.\)
=> \(\left[ \begin{array}{l}x=0\\x=2\end{array} \right.\)
c)
`(x+5)(x-6) = 0`
=> \(\left[ \begin{array}{l}x+5=0\\x-6=0\end{array} \right.\)
=> \(\left[ \begin{array}{l}x=-5\\x=6\end{array} \right.\)
d)
`(x-1)(x+3) = 0`
=> \(\left[ \begin{array}{l}x-1=0\\x+3=0\end{array} \right.\)
=> \(\left[ \begin{array}{l}x=1\\x=-3\end{array} \right.\)
