We know that
Velocity is given by the rate of change of position w.r.t time
[tex]\\ \sf\longmapsto v=\dfrac{dx}{dt}[/tex]
[tex]\\ \sf\longmapsto vdt=dx[/tex]
[tex]\\ \sf\longmapsto (u+at)dt=dx[/tex]
[tex]\\ \sf\longmapsto u{\displaystyle{\int}_0^t}dt+a{\displaystyle{\int}_0^t}dt={\displaystyle{\int}^x_{x_0}}dx[/tex]
[tex]\\ \sf\longmapsto ut+\dfrac{1}{2}at^2=(x-x_0)[/tex]
[tex]\\ \sf\longmapsto x=x_0+ut+\dfrac{1}{2}at^2[/tex]