Sol. $$ \begin{aligned} & F=a x^2+b t^{1 / 2} \\ & {[\mathrm{a}]=\frac{[\mathrm{F}]}{\left[\mathrm{x}^2\right]}=\left[\mathrm{M}^1 \mathrm{~L}^{-1} \mathrm{~T}^{-2}\right]} \\ & {[\mathrm{b}]=\frac{[\mathrm{F}]}{\left[\mathrm{t}^{1 / 2}\right]}=\left[\mathrm{M}^1 \mathrm{~L}^1 \mathrm{~T}^{-5 / 2}\right]} \\ & {\left[\frac{b^2}{a}\right]=\frac{\left[\mathrm{M}^2 \mathrm{~L}^2 \mathrm{~T}^{-5}\right]}{\left[\mathrm{M}^1 \mathrm{~L}^{-1} \mathrm{~T}^{-2}\right]}=\left[\mathrm{M}^1 \mathrm{~L}^3 \mathrm{~T}^{-3}\right]} \end{aligned} $$