eng Science and Education Publishing Applied Mathematics and Physics 2333-4886 2017-08-16 5 3 95 98 10.12691/amp-5-3-3 AMP2017533 article Jianbing Cao caocjb@163.com 1 Department of Mathematics, Henan Institute of Science and Technology, Xinxiang, China In this paper, we establish the general solution of a 2-variable quadratic functional equation f(2x+y,2z+w)=f(x+y,z+w)-f(x-y,z-w)+4f(x,z)+f(y,w) and prove the generalized Hyers-Ulam stability of this functional equation. http://pubs.sciepub.com/amp/5/3/3/amp-5-3-3.pdf solution stability quadratic functional equation