Find $\frac{dy}{dx}$ and $\frac{d^{2}y}{d{x}^2}.$

$x=t^2+9,y=t^2+7t$

$\frac{dy}{dx}=$

$\frac{d^{2}y}{d{x}^2}=$

For which values of $t$ is the curve concave upward? $($Enter your answer using interval notation.$)$