Answer
The function f is not positive for $x\geq1$; therefore, the Integral Test cannot be applied.
Work Step by Step
$Let f(x) = \frac{(-1)^{x}}{x}$ where $f(n) = a_n$
In order to apply the Integral Test, f(x) must be positive, decreasing and continuous for all $x\geq1$.
$f(1) = -1 $
Since f is not positive for all $x\geq1$, the Integral Test can not be used.
