1. Given the inequality $a x+3 \geqslant 0$ has positive integer solutions of $1,2,3$. Then the range of values for $a$ is $\qquad$ .
Ni.1. $-1 \leqslant a<-\frac{3}{4}$.
From $a x+3 \geqslant 0$, we get $a x \geqslant-3$.
Obviously, $a<0$ (otherwise, the positive integer solutions of the original inequality would not be just $1,2,3$). Therefore, $x \leqslant-\frac{3}{a}$.
According to the problem, $3 \leqslant-\frac{3}{a}<4$. Solving this, we get $-1 \leqslant a<-\frac{3}{4}$.