The velocity of a wave is given by $v = \sqrt{\frac{T}{\mu}} + ax^2$, where $T$ is tension, $\mu$ is linear density, and $x$ is displacement. What are the dimensions of $a$?

A physical quantity u is given by the relation $u = \frac{{{B^2}}}{{2{{\rm{\mu }}_0}}}$ here, B=magnetic field strength ${{\rm{\mu }}_0} =$ magnetic permeability of vacuum.