\[\begin{array}{l}
\frac{{4x}}{{{x^2} + x + 3}} + \frac{{5x}}{{{x^2} - 5x + 3}} = - \frac{3}{2}\\
DK................\\
y = {x^2} + x + 3 \to y > 0\\
\to \frac{{4x}}{y} + \frac{{5x}}{{y - 6x}} = \frac{{ - 3}}{2}\\
\to 8x\left( {y - 6x} \right) + 10xy = - 3y\left( {y - 6x} \right)\\
\to 8xy - 48{x^2} + 10xy = - 3{y^2} + 18xy\\
\to 48{x^2} = 3{y^2}\\
\to 4|x| = y....................................
\end{array}\]