(b) $v = v_{0} + gt + ft^{2}$
Or $\frac{dx}{dt} = v_{0} + gt + ft^{2}$
Or $\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ dx = \left( v_{0} + gt + ft^{2} \right)\ dt$
So, $\ \ \ \ \ \ \ \ \ \ \int_{0}^{x}{dx} = \int_{0}^{1}{\left( v_{0} + gt + ft^{2} \right)\ dt}$
Or $\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ x = v_{0} + \frac{g}{2} + \frac{f}{3}$