7 A particle \(P\) moves with constant acceleration \(( - 4 \mathbf { i } + 2 \mathbf { j } ) \mathrm { ms } ^ { - 2 }\). At time \(t = 0\) seconds, \(P\) is moving with velocity \(( 7 \mathbf { i } + 6 \mathbf { j } ) \mathrm { ms } ^ { - 1 }\).
- Determine the speed of \(P\) when \(t = 3\).
- Determine the change in displacement of \(P\) between \(t = 0\) and \(t = 3\).