Write the dimensions of a and b in the relation, P=b-x2at, where P is power, x is distance and t is time.
[a]==M-2 L0 T2,[b]=M1 L2 T0
[a]==M-1 L0 T2,[b]=M2 L2 T0
[a]==M-1 L0 T2,[b]=M1 L2 T0
[a]==M-1 L0 T2,[b]=M0 L2 T0
The given equation can be written as, Pat=b-x2
Now,
[Pat]=[b]=x2 or [b]=x2=M0 L2 T0 and [a]=x2[Pt]=L2ML2 T-3[T]=M-1 L0 T2