Đáp án:+Giải thích các bước giải:

`4) (2x - 3)(3/4x + 1 ) = 0 `

\(\left[ \begin{array}{l}2x - 3 =0\\\dfrac{3}{4}x + 1 = 0\end{array} \right.\) 

\(\left[ \begin{array}{l}x=\dfrac{3}{2}\\x=\dfrac{-4}{3}\end{array} \right.\) 

Vậy `x ∈ { 3/2 ; -4/3} `

`5) (3 - 2x )(4/7x + 2 ) = 0 `

\(\left[ \begin{array}{l}3-2x=0\\\dfrac{4}{7}x +2 = 0 \end{array} \right.\) 

\(\left[ \begin{array}{l}x=\dfrac{3}{2}\\x=\dfrac{-7}{2}\end{array} \right.\) 

Vậy `x ∈ { 3/2 ; -7/2}`

`6) ( 5 - 7x)(3/7 - 3x) = 0` 

\(\left[ \begin{array}{l}5-7x=0\\\dfrac{3}{7}-3x = 0 \end{array} \right.\) 

\(\left[ \begin{array}{l}x=\dfrac{5}{7}\\x=\dfrac{1}{7}\end{array} \right.\) 

Vậy` x ∈ { 5/7 ; 1/7} `

`@Kwan`