The potential energy of a particle changes with distance \( x \) from a fixed origin as \( V=\dfrac{A\sqrt{x}}{x+B} \), where \( A \) and \( B \) are constant with appropriate dimensions. The dimensions of \( AB \) are ______.
\( [M^1 L^{5/2} T^{-2}] \)
\( [M^{3/2} L^{5/2} T^{-2}] \)
\( [M^1 L^{2} T^{-2}] \)
\( [M^1 L^{7/2} T^{-2}] \)