9.104. For what values of $a$ does the quadratic trinomial $a x^{2}-7 x+4 a$ take negative values for any real values of $x$?
Solution.

The quadratic trinomial $a x^{2}-7 x+4 a\frac{49}{16}, \\ a<0\end{array} \Leftrightarrow\left(a<-\frac{7}{4}\right)\right.\right.$.

Answer: $a \in\left(-\infty ;-\frac{7}{4}\right)$.