Final Answer:
The integral
is improper when
and

Step-by-step explanation:
The given integral
is improper when the power
in the denominator leads to convergence issues. For an integral to be proper, it should converge to a finite value.
If
, the integral is improper because it involves division by zero when
. In this case, the function is not defined at \( x = 0 \), leading to a singularity and making the integral improper.
Additionally, when
the integral is improper due to the presence of a logarithmic singularity at
. The logarithmic singularity causes the integral to diverge.
For all other values of
, the integral is proper and converges within the given limits of integration (0 to 6). Therefore, the final answer is that the integral is improper when
and
.