TeX source:

\lambda\vec{a}^{\,T}\cdot\left(\vec{b}\times\vec{c}\right) = \vec{a}^{\,T}\cdot\left(\lambda\vec{b}\times\vec{c}\right) = \vec{a}^{\,T}\cdot\left(\vec{b}\times\lambda\vec{c}\right) = \vec{a}^{\,T}\cdot\left(\vec{b}\times\vec{c}\right)\cdot\lambda