Many difference equations of the form
$ x_{n+k} = f(x_{n+k-1}, \ldots, x_n), \quad n\in {\mathbb N}, $
where $ k\in {\mathbb N} $, model some phenomena in nature and society. The most interesting cases usually occur when the function $ f $ satisfies the condition $ f(x, \ldots, x) = x $ on its domain of definition. Because of this the difference inequalities $ x_{n+k}\le f(x_{n+k-1}, \ldots, x_n) $ and $ x_{n+k}\ge f(x_{n+k-1}, \ldots, x_n) $ are of some interest. If $ f $ is a smooth function, then it can be approximated by a linear function. Motivated by some concrete examples, here we mostly consider the sequences that satisfy the linear difference inequality
$ \begin{align*} \sum\limits_{j = 1}^ka_jx_{n+l-j}\ge 0, \quad n\in {\mathbb N}_0, \end{align*}$
where $ k\in {\mathbb N}_2 $, $ l\in {\mathbb N}_0, $ and the coefficients $ a_j\in {\mathbb R}, $ $ j = \overline{2, k-1} $, $ a_1, a_k\in {\mathbb R}\setminus\{0\}, $ satisfy the condition $ \sum_{j = 1}^ka_j = 0. $
Citation: Stevo Stević. Linear difference inequalities with constant coefficients with the sum equal to zero[J]. AIMS Mathematics, 2025, 10(11): 26744-26766. doi: 10.3934/math.20251176
Many difference equations of the form
$ x_{n+k} = f(x_{n+k-1}, \ldots, x_n), \quad n\in {\mathbb N}, $
where $ k\in {\mathbb N} $, model some phenomena in nature and society. The most interesting cases usually occur when the function $ f $ satisfies the condition $ f(x, \ldots, x) = x $ on its domain of definition. Because of this the difference inequalities $ x_{n+k}\le f(x_{n+k-1}, \ldots, x_n) $ and $ x_{n+k}\ge f(x_{n+k-1}, \ldots, x_n) $ are of some interest. If $ f $ is a smooth function, then it can be approximated by a linear function. Motivated by some concrete examples, here we mostly consider the sequences that satisfy the linear difference inequality
$ \begin{align*} \sum\limits_{j = 1}^ka_jx_{n+l-j}\ge 0, \quad n\in {\mathbb N}_0, \end{align*}$
where $ k\in {\mathbb N}_2 $, $ l\in {\mathbb N}_0, $ and the coefficients $ a_j\in {\mathbb R}, $ $ j = \overline{2, k-1} $, $ a_1, a_k\in {\mathbb R}\setminus\{0\}, $ satisfy the condition $ \sum_{j = 1}^ka_j = 0. $
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