## Calculus 8th Edition

$f(x)=\frac{4}{x^3}$ is not continuous in $(-1,2)$, and hence FTC-2 cannot be applied.
According to the fundamental theorem of calculus, $\int_a^bf(x)dx = F(b)-F(a)$, where $F$ is the antiderivative of $f$ or $F'=f$, provided that $f$ is continuous in $(a, b)$. Here, $\frac{4}{x^3}$ is not continuous in $(-1,2)$ and as an infinite discontinuity at $x=0$.