Parametric in $t$

Given that $x = \dfrac {t^2}2 a(t)$ and $y = t \cdot v(t)$ , where $a(t)$ and $v(t)$ are functions of $t$ . Find the value of $\dfrac{dy}{dx}$ at $t = 1$ if when $t = 1$ , $y = 2$ , $a(1) = 2v(1) , a'(1) = v'(1) = x$ .