82 To make the inequality $0 \leqslant x^{2}+a x+5 \leqslant 4$ have exactly one solution, then $a=$
82 . . Let $y=x^{2}+a x+5$, the graph of this function is a parabola opening upwards, so there is only one solution to the inequality when the vertex of the parabola is on the line $y=4$, hence
$$
5-\frac{a^{2}}{4}=4
$$

Solving for $a$ gives $a= \pm 2$.