An existence result for a class of (p(x),q(x))-Laplacian system via sub-supersolution method Saleh Shakeri Department of Mathematics, Ayatollah Amoli Branch, Islamic Azad University, Amol, P. O. Box 678, Iran author text article 2021 eng This study concerns the existence of positive solution for the following nonlinear boundary value problem\begin{gather*}-\Delta_{p(x)} u= a(x)h(u) + f(v) \quad\text{in }\Omega\\-\Delta_{q(x)} v=b(x)k(v) + g(u) \quad\text{in }\Omega\\u=v= 0 \quad\text{on } \partial \Omega\end{gather*}where $p(x),q(x) \in C^1(\mathbb{R}^N)$ are radial symmetric functions such that $\sup|\nabla p(x)| < \infty,$ $\sup|\nabla q(x)|<\infty$ and $1 < \inf p(x) \leq \sup p(x) <\infty,1 < \inf q(x) \leq \sup q(x) < \infty$, and where $-\Delta_{p(x)} u = -\mathop{\rm div}|\nabla u|^{p(x)-2}\nabla u,-\Delta_{q(x)} v =-\mathop{\rm div}|\nabla v|^{q(x)-2}\nabla v$ respectively are called $p(x)$-Laplacian and $q(x)$-Laplacian, $\Omega = B(0 , R) = \{x | |x| < R\}$ is a bounded radial symmetric domain, where $R > 0$ is a sufficiently large constant. We discuss the existence of positive solution via sub-supersolutions without assuming sign conditions on $f(0)$ and $g(0)$. Mathematical Analysis and its Contemporary Applications A.I.A University Publishing Group. 2716-9890 3 v. 4 no. 2021 1 8 http://www.macajournal.com/article_685401_bf81051cb14c0238acbe5412b52fd812.pdf dx.doi.org/10.30495/maca.2021.1937515.1024 On closedness of convolution of two sets Seyyed Mohammad Tabatabaie Department of Mathematics, University of Qom, Qom, Iran author text article 2021 eng In this note, we give an abstract version of the fact that convolution of two closed and compact subsets of a hypergroup is a closed set. Mathematical Analysis and its Contemporary Applications A.I.A University Publishing Group. 2716-9890 3 v. 4 no. 2021 9 12 http://www.macajournal.com/article_685578_0667a5097e65cd0dc09860c42fe2a77f.pdf dx.doi.org/10.30495/maca.2021.1935853.1020 On a nonlinear abstract second-order integrodifferential equation part I Mohammed Hussain H.no 3-8-44\slash2(1-25-176), Manzoorpura, Near Shahgunj, Aurangabad (431001), Maharashtra, India author text article 2021 eng The object of this paper is to study the existence, uniqueness and continuation of the solutions of nonlinear second-order integrodifferential equations. In the theory of infinitesimal generator of $C_0$- semigroup in a Banach space, the fixed point theorems of Schauder and Banach are used to establish our main results. Mathematical Analysis and its Contemporary Applications A.I.A University Publishing Group. 2716-9890 3 v. 4 no. 2021 13 24 http://www.macajournal.com/article_685579_252fa30ee6eae90f5a07fdad068b1c66.pdf dx.doi.org/10.30495/maca.2021.1936023.1022 Numerical solution of a coupled system of fractional order integro differential equations by an efficient numerical method based on the second kind Chebyshev polynomials Mohammad Hossein Derakhshan Department of Industrial Engineering, Apadana Institute of Higher Education, Shiraz, Iran author text article 2021 eng In this paper, an efficient numerical method based on operational matrices of the second kind Chebyshev polynomials is used for the solution of a coupled system of fractional-order integrodifferential equations that the fractional derivative is given in Caputo's sense. The operational matrices of the second kind Chebyshev polynomials reduce the given equations to a system of linear algebraic equations. An approximate solution is calculated by extending the functions in terms of the second kind Chebyshev polynomials and applying operational matrices. Unknown coefficients are obtained by solving the final system of linear equations. Also, convergence analysis and error bound of the solution are studied in this paper. Moreover, to check the reliability and accuracy of the given method. The numerical examples have been shown and the results of the described method are compared with the Haar wavelet method. The obtained results authenticate that the displayed method is effortless to analyze and perform such types of problems. All methods for the proposed method are applied in MATLAB (R2020b) software. Mathematical Analysis and its Contemporary Applications A.I.A University Publishing Group. 2716-9890 3 v. 4 no. 2021 25 40 http://www.macajournal.com/article_685644_23f14b286fa615fb690c448b625b9a9b.pdf dx.doi.org/10.30495/maca.2021.1938222.1025 Multiplicity results for the nonlinear p-Laplacian fractional boundary value problems Tawanda Gallan Chakuvinga Department of Mathematics, Ege University, 35100 Bornova, Izmir, Turkey author Fatma Serap Topal Department of Mathematics, Ege University, 35100 Bornova, Izmir, Turkey author text article 2021 eng This paper investigates the existence of single and multiple positive positive solutions of fractional differential equations with p-Laplacian by means of the Green's function properties, the Guo-Krasnosel'skii fixed point theorem, the monotone iterative technique accompanied by established sufficient conditions and the Leggett-Williams fixed point theorem. Additionally, the main results are illustrated by some examples to show their validity. Mathematical Analysis and its Contemporary Applications A.I.A University Publishing Group. 2716-9890 3 v. 4 no. 2021 41 62 http://www.macajournal.com/article_686168_4d65d67d764c3138e2e501d1fba96748.pdf dx.doi.org/10.30495/maca.2021.1938349.1026 Bifuzzy d-algebras under norms Rasul Rasuli Department of Mathematics, Payame Noor University, Tehran, Iran. author text article 2021 eng In this paper, by using norms (t-norms and t-conorms), we introduce the notions of bifuzzy d-algebras and bifuzzy d-ideals of d-algebras and investigate several interesting properties. Next, we consider their intersection and product. Finally, we obtain some results about them under d-algebra homomorphisms. Mathematical Analysis and its Contemporary Applications A.I.A University Publishing Group. 2716-9890 3 v. 4 no. 2021 63 83 http://www.macajournal.com/article_685803_34880c5e15307e9ddc2ffe920f7829e7.pdf dx.doi.org/10.30495/maca.2021.1938454.1027