Answer
The electron reaches a turning point at $~~x = 1.75~cm$
Work Step by Step
We can find the total energy at $x = 4.5~cm$:
$E = K+U$
$E = 3.00~eV+(-1e)(6.00~V)$
$E = -3.00~eV$
By conservation of energy, the electron can reach an electric potential as low as $3.00~V$
Since the left side of the region has an electric potential of $2.00~V$, the electron can not escape out the left side of the region.
On the graph, we can see that the electric potential is $3.00~V$ at $x = 1.75~cm$
The electron reaches a turning point at $~~x = 1.75~cm$.
