From Mechanics

We assume the origin is att the point of tacke off which means \displaystyle \ \ \mathbf{ r}_{0}=0.

Also we have \displaystyle \mathbf{a}=\mathbf{i}+4\mathbf{j},\ \ \displaystyle \mathbf{u}=80\mathbf{i}\ \.

Using \displaystyle \mathbf{v}=\mathbf{u}+\mathbf{a}t\ \ gives at time \displaystyle t,

\displaystyle \mathbf{v}=80\mathbf{i}+(\mathbf{i}+4\mathbf{j})t\ \ or

\displaystyle \mathbf{v}=(80+t\ )\mathbf{i}+4t\ \mathbf{j}