Làm giúp đê các ông bà cô dì chú bác ơi Tìm x nha:

` 3)(2/5 x-1/2)(1/3+(-2)/3:x)=0 `

` => ` \(\left[ \begin{array}{l}\dfrac{2}{5}x-\dfrac{1}{2}=0\\\dfrac{1}{3}+\dfrac{-2}{3}:x=0\end{array} \right.\) 

` => ` \(\left[ \begin{array}{l}\dfrac{2}{5}x=\dfrac{1}{2}\\\dfrac{-2}{3}:x=\dfrac{-1}{3}\end{array} \right.\) 

` => ` \(\left[ \begin{array}{l}x=\dfrac{5}{4}\\x=2\end{array} \right.\) 

` =>x in {5/4;2} `

` 4)(x^2+4)(2x-5)=0 `

` => ` \(\left[ \begin{array}{l}x^2+4=0\\2x-5=0\end{array} \right.\) 

` => ` \(\left[ \begin{array}{l}x∈∅.Vô lý x^2+4≥4∀x\\2x=5\end{array} \right.\) ` =>x=5/2 `