Probability density function is given by
.
Find second derivative of the probability density function with respect to
.
Consider
.
Differentiate on each side with respect to
.

.
Differentiate on each side with respect to
.


Find the inflection points by equating the
.

Exponential function can never be zero.
\

Therefore, probability density function has inflection points at
.
Probability density function has inflection points at
.