Question:

$\vec{u}_1,\vec{u}_2,\vec{u}_3$ coplanar and $\vec{v}_1,\vec{v}_2,\vec{v}_3$ also coplanar (expressions in $a,b,c$). Then $6(a+b+c)$ is equal to

Step-by-Step Solution

Key Concept: First coplanarity: $a+b+c=2+abc$. Second: after row operations gives $abc=0$. Therefore $a+b+c=2$.

$6(a+b+c)=12$.

Correct Answer: 3