Câu 2:
Cho f:R3→R3f:\mathop R\nolimits^3 \to \mathop R\nolimits^3f:R3→R3 , Tập V tất cả (x1,x2,x3)(\mathop x\nolimits_1 ,\mathop x\nolimits_2 ,\mathop x\nolimits_3 )(x1,x2,x3)f(x1,x2,x3)=(x1+x2+x3,x1+x2+x3,x1−x2−x3)f(\mathop x\nolimits_1 ,\mathop x\nolimits_2 ,\mathop x\nolimits_3 ) = (\mathop x\nolimits_1 + \mathop x\nolimits_2 + \mathop x\nolimits_3 ,\mathop x\nolimits_1 + \mathop x\nolimits_2 + \mathop x\nolimits_3 ,\mathop x\nolimits_1 - \mathop x\nolimits_2 - \mathop x\nolimits_3 )f(x1,x2,x3)=(x1+x2+x3,x1+x2+x3,x1−x2−x3) thỏa f(x1,x2,x3)f(\mathop x\nolimits_1 ,\mathop x\nolimits_2 ,\mathop x\nolimits_3 )f(x1,x2,x3) =0 là:
