Consider Two Vectors $\vec { v } = 5 \vec { i } - \vec { j } + 3 \vec { k }$

Essay

Consider two vectors $\vec { v } = 5 \vec { i } - \vec { j } + 3 \vec { k }$ and $\vec { w } = a \vec { i } + a \vec { j } - \vec { k }$ .For what value(s)of a are $\vec { v }$ and $\vec { W }$ perpendicular?