An object, which is at the origin at time t=0, has initial velocity v0= (-14.0i - 7.0j)m/s and constant acceleration a=(6.0i + 3.0j)m/s^2..

find the position x where the object comes to rest (momentarily).
express your answer in terms of the unit vectors i and j.

r=

I am pretty sure the first thing we should do is to integrate acceleration into velocity
And we will have: 
Then calculate v :
As you can see, velocity is zero and none of the objects is moving. It happens when  t=7/3 which means we can calculate this in the way we did (integrating) :

The product is p(0) = 0 that makes us to reduce vector function to

xy+6xy

=7by

hope this helps you