|\table 2 b c-a^{2} , c^{2} , b^{2} ; c^{2} , 2 c a-b^{2} , a^{2} ; b^{2} , a^{2} , 2 a b-c^{2}|=(a^{3}+b^{3}+c^{3}+k a b c)^{2}, then k is equal to