Let be three non zero vectors such that then where is ........

Let $\vec{a},\vec{b},\vec{c}$ be three non-zero vectors such that $\vec{a}+\vec{b}+\vec{c}=0$ , then $\lambda \vec{b}\times +\vec{a}+\vec{b}\times \vec{c}\times \vec{a}=\vec{0}$ , where $\lambda$ is