If y represents pressure and x represents velocity gradient, then the dimensions of d2ydx2 are
M L-1 T-2
M2 L-2 T-2
M L-1 T0
M2 L-2 T-4
As,
d2sdt2is acceleration or ms2or LT-2
In the similar way,
d2ydx2=yx2=ML-1 T-2T-12=ML-1 T0