Question

Could someone please point out my error solving the following problem involving a cross and dot product.

Find u (dot) (v x w)
u=<2,-3,1>
v=<4,1,-3>
w=<0,1,5>

My answer=-40
Answer in book=80

Answer 1

v x w = <8,20,4>

u (dot) <8,20,4>=<2,-3,1> (dot) <8,20,4>=-40

Answer 2

$$\vec{v}\times\vec{w}=(5+3,0-20,4-0)=(8,-20,4)\\\vec{u}\cdot(\vec{v}\times\vec{w})=(2,-3,1)\cdot(8,-20,4)=16+60+4=80$$

Answer 3

You messed up the sign of your middle component when computing your cross product!