7. Regulation: For $x \in \mathbf{R}$, if and only if $n \leqslant x<n+1\left(n \in \mathbf{N}^{*}\right)$, then $[x]=n$. Then the solution set of the inequality $4[x]^{2}-36[x]+45 \leqslant 0$ is $\qquad$.
Since $[x] \in \mathbf{N}^{*}$, and $4[x]^{2}-36[x]+45 \leqslant 0 \Rightarrow 2 \leqslant[x] \leqslant 7 \Rightarrow 2 \leqslant x<8$, the solution set of the inequality $4[x]^{2}-36[x]+45 \leqslant 0$ is $[2,8)$.