9.073. $a^{4}+a^{3}-a-1<0$.

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9.073. $a^{4}+a^{3}-a-1<0$.
Solution.

Grouping, we get

$$
a^{3}(a+1)-(a+1)0$ for $a \in R$, so it is equivalent to the inequality $(a+1)(a-1)<0$. Using the number line, we get $a \in(-1 ; 1)$.

![](https://cdn.mathpix.com/cropped/2024_05_22_fa9db84b44b98ec0a5c7g-543.jpg?height=158&width=488&top_left_y=1245&top_left_x=424)

Answer: $\quad a \in(-1 ; 1)$