a) \(\left(x+5\right)\left(x-4\right)=0\)
\(\Rightarrow\hept{\begin{cases}x=-5\\x=4\end{cases}}\)
b) \(\left(x-1\right)\left(x-3\right)=0\)
\(\Rightarrow\hept{\begin{cases}x=1\\x=3\end{cases}}\)
c) \(\left(3-x\right)\left(x-3\right)=0\Rightarrow x=3\)
d) \(x\left(x+1\right)=0\Rightarrow\hept{\begin{cases}x=0\\x=-1\end{cases}}\)
(x+5)(x-4) = 0
\(\orbr{\begin{cases}x+5=0\\x-4=0\end{cases}}\)
\(\orbr{\begin{cases}x=0-5\\x=0+4\end{cases}}\)
\(\orbr{\begin{cases}x=-5\\x=4\end{cases}}\)