Sebuah sifat topologi selain dapat dimiliki oleh suatu ruang topologi juga dapat dimiliki oleh subruang dari ruang topologi tersebut. Pada makalah ini akan dibahas tentang aksioma keterhitungan pertama pada topologi hasil kali ruang metrik kerucut, khususnya pada subruang tutup. Pembahasan dilakukan dengan menunjukkan bahwa setiap elemen dari setiap subruang tutup dari topologi hasil kali dua ruang metrik kerucut memiliki basis lokal terhitung. Hasilnya adalah setiap subruang tutup dari topologi hasil kali ruang metrik kerucut juga memenuhi aksioma keterhitungan pertama. Dengan kata lain keterhitungan pertama bersifat hereditas lemah.

Several factors can affect the amount of investment credit issued by the bank. This study discusses the effect of interest rates, inflation rates, capita income, and the number of medium-large industries on the number of investment loans, using the method of linear regression analysis. The independent variables examined to determine the influence of each and all the independent variables on the number of investment loans in commercial banks, namely interest rates, inflation rates, capita income, and the number of medium-large industries using the parameter estimation method, OLS (Ordinary Least Square).

This paper discusses Green’s matrix of nonlinear boundary value problem of first-order differential system with rectangular coeffisients, especially about its properties. In this case, the differential equation of the form  with boundary conditions of the form   and  which  is a real  matrix with  whose entries are continuous on  and . ,  are nonsingular matrices such that  and  are constant vectors. To get the Green’s matrix and the assosiated generalized Green’s matrix, we change the boundary condition problem into an equivalent  differential equation by using the properties of the  Moore-Penrose generalized inverse, then  its solution is found by using method of variation of parameters. The last we prove  that the defined matrices  satisfy the properties of green’s function. The result is the corresponding the Green’s matrix and the assosiated generalized Green’s matrix have the property of Green’s functions with the jump-discontinuity.

This paper discusses some operations on mixed monotone operator in Banach space, especially addition an multiplication operations. We will prove the sum and product of two mixed monotone operators. The proof using some relevant definitions. The result is the sum o of them is a mixed monotone operator and the product is  too if both  satisfy some conditions

First order Space-Time Autoregressive model is one of the models which involves location and time. STAR(1;1) model stationary can be used to forecast future observation at a location based on one previous time of its own location and the spatial neighborhood. STAR(1;1) model on petroleum productivity data in Balongan, Indramayu, West Java with eigenvalue less than 1. It indicates that STAR (1;1) model on petroleum productivity data in Balongan, Indramayu, West Java meets the stationary requirement