Giải thích các bước giải:
a) `7x-4=0`
`=> 7x=4`
`=> x = 4/7`
b) `3x - 3(x-2)= 0`
`=> 3(x-2)=3x`
`=> x-2 = x`
`=> 0x = 2 (KTM)`
`=>` PT vô nghiệm
c) `(x-1)(5x+1)=0`
`=>` \(\left[ \begin{array}{l}x-1=0\\5x+1=0\end{array} \right.\) `=>` \(\left[ \begin{array}{l}x=1\\5x=-1\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}x=1\\x=\frac{-1}{5}\end{array} \right.\)
d) `x^3 - 5x^2 = 0`
`=> x^2 ( x - 5)=0`
`=>` \(\left[ \begin{array}{l}x^2=0\\x-5=0\end{array} \right.\) `=>` \(\left[ \begin{array}{l}x=0\\x=5\end{array} \right.\)
