Find all integers $a$, $b$, $c$ and $d$ such that $$a^2+5b^2-2c^2-2cd-3d^2=0$$
Problem
Source: Regional Olympiad - Federation of Bosnia and Herzegovina 2013
Tags: number theory, equation
Source: Regional Olympiad - Federation of Bosnia and Herzegovina 2013
Tags: number theory, equation
Find all integers $a$, $b$, $c$ and $d$ such that $$a^2+5b^2-2c^2-2cd-3d^2=0$$