Answer
$s(t)=16t^2-2t+1$
Work Step by Step
Here, $s=\dfrac{ds}{dt}=32t-2$, thus the general form of the function is: $s(t)=16t^2-2t+C$
Since we have $s(0.5)=4$
Therefore, $s(0.5)=4 \implies 4=16(0.5)^2-2(0.5)+C$
Thus, $C=1$
Hence, $s(t)=16t^2-2t+1$