Motion

Two cars A and B start from a point at the same time in a straight line and their positions are represented by \(\mathrm{R}_{\mathrm{A}}(\mathrm{t})=\) at \(+\mathrm{bt}^2\) and \(\mathrm{R}_{\mathrm{B}}(\mathrm{t})=x \mathrm{t}-\mathrm{t}^2\). At what time do the cars have same velocity?