Answer
(a) See the graph.
(b) $y=\frac{1}{x},~~x\gt0,~~y\gt0$
Work Step by Step
(a)
$t=0$:
$x=e^0=1$
$y=e^0=1$
Point: $(1,1)$
When $t→+∞$, $x→0$ and $y→+∞$.
When $t→-∞$, $x→∞$ and $y→0$. So, $x\gt0$ and $y\gt0$
(b)
$y=e^t$
$x=e^{-t}$
$x=\frac{1}{y}$
$y=\frac{1}{x}$