​ @CPhill

I think heureka answered this here :

https://web2.0calc.com/questions/correct#r2

The vector in the opposite direction of  \(\vec u\)  is  \(-\vec u\)  .

The unit vector in the same direction of  \(\vec u\)  is  \(\frac{\vec u}{|\vec u|}\)  which is  \(\frac{\vec u}{7}\)  .

So the unit vector in the opposite direction of  \(\vec u\)  is  \(-\frac{\vec u}{7}\)  .