A particle P P\,P moves along a straight line with constant acceleration a a\,a m s−2^{-2}−2.
P P\,P passes the point A A\,A with speed u u\,u m s−1^{-1}−1.
Three seconds after passing AAA, the particle passes the point BBB, where AB=21AB = 21AB=21 metres.
Five seconds after passing AAA, the particle passes the point CCC, where AC=45AC = 45AC=45 metres.
Find the value of u u\,u and the value of aaa.