... 2 Journal of Inequalities and Applications in the spaces of generalized functions. Also, we obtain the general solution and prove the Hyers-Ulam stability of 1.1 in the spaces of generalized ... that have the quadraticproperty,” Journal of Mathematical Analysis and Applications, vol. 222, no. 1, pp. 126–137, 1998.17 L. H¨ormander, The Analysis of Linear Partial Differential Operators. ... Functional Equations in Several Variables , Progress in Nonlinear Differential Equations and Their Applications, 34, Birkh¨auser, Boston, Mass, USA, 1998.10 Journal of Inequalities and ApplicationsOn...