Probably easy proof for you guys

[benhou]

Homework Statement

Prove if \vec{x}\times\vec{v}=\vec{x}\times \vec{u}, then \vec{v}=\vec{u}
where \vec{x}\neq \vec{0}

2. The attempt at a solution

Use the definition of cross product and tried to reduce it.

 

[LCKurtz]

That is false as stated. Let x = <-2, 3, 1>, u = <1,2,3>, v = < 3,-1,2>. Then x cross u and x cross v are both <7,7,-7>. So your first step in solving the problem is to state it correctly.