Write the dimensions of a × b in the relation E=b−x2at, where E is the energy, x is the displacement and t is time.
M−1L2T1
Here [b] and [x]2=L2 have same dimensions.
Also [a]=[x]2[E]×[t] =L2(ML2T−2)T =M−1T1
a×b=[M−1L2T1]
hence correct answer is (b).