Solve[ Det[ { {0, (a/c)^2, (a/c)^2, (b/c)^2, 1}, {(a/c)^2, 0, (2 (a/c))^2, 1, 1}, {(a/c)^2, (2 (a/c))^2, 0, 1, 1}, {(b/c)^2, 1, 1, 0, 1}, {1, 1, 1, 1, 0} } ] == 0, c ]