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

c) $\left(3\mathrm{x}-1\right)\left(\frac{-1}{2}\mathrm{x}+5\right)=0$

• Trường hợp 1:

3x – 1 = 0

3x = 1

$\mathrm{x}=\frac{1}{3}$ 

• Trường hợp 2:

$\begin{array}{l}\frac{-1}{2}\mathrm{x}+5=0\\ \frac{-1}{2}\mathrm{x}=-5\\ \mathrm{x}=-5:\left(\frac{-1}{2}\right)\\ \mathrm{x}=5.\frac{2}{1}\\ \mathrm{x}=10\end{array}$

Vậy giá trị x cần tìm là $\mathrm{x}\in \left\{\frac{1}{3};10\right\}$.