[tex]\displaystyle\bf\\\frac{x^{2} +3x}{4}-\frac{x}{8} =0 \\\\\\\frac{x^{2} +3x}{4}\cdot 8-\frac{x}{8}\cdot 8 =0\cdot 8\\\\\\2\cdot(x^{2} +3x)-x=0\\\\2x^{2} +6x-x=0\\\\2x^{2} +5x=0\\\\x\cdot(2x+5)=0\\\\\\\left[\begin{array}{ccc}x=0\\2x+5=0\end{array}\right \\\\\\\left[\begin{array}{ccc}x=0\\2x=-5\end{array}\right \\\\\\\left[\begin{array}{ccc}x_{1} =0\\x_{2} =-2,5\end{array}\right \\\\\\Otvet \ : \ 0 \ ; \ -2,5[/tex]