New Indefinite Summation Formulas and Some Applications

Abstract

In this paper, we introduce a novel indefinite summation $\sum_{t} f(t)$ (or antidifference $\Delta ^{-1}f(t) $ ) formula for any given function $f$. We apply the indefinite summation formula to calculate a particular solution to a nonhomogeneous linear difference equation of the form $$ y(x+h)-\lambda y(x)=f(x),\quad h > 0,\quad \lambda \neq 0, $$ and also to solve a linear difference inequality of the form $$ y(x+h)-\lambda y(x) \geq 0,\quad h > 0,\quad \lambda \neq 0. $$ Furthermore, we apply the formula to determine a particular solution to a difference equations of the form $$ \Phi(E)y(t)=f(t), $$ and in solving a linear difference inequality of the form, $$ \Phi(E)y(t)\geq 0, $$ where $ \Phi(E) $ is some linear difference operator. We show how the antidifference of a function $f$ calculated with the current formula is related to the already existing result and establish the corresponding identity.