  In this paper, we address the maximum number of vertices of induced forests
in subcubic graphs with girth at least four or five. We provide a unified
approach to prove that every 2-connected subcubic graph on $n$ vertices and $m$
edges with girth at least four or five, respectively, has an induced forest on
at least $n-\frac{2}{9}m$ or $n-\frac{1}{5}m$ vertices, respectively, except
for finitely many exceptional graphs. Our results improve a result of Liu and
Zhao and are tight in the sense that the bounds are attained by infinitely many
2-connected graphs. Equivalently, we prove that such graphs admit feedback
vertex sets with size at most $\frac{2}{9}m$ or $\frac{1}{5}m$, respectively.
Those exceptional graphs will be explicitly constructed, and our result can be
easily modified to drop the 2-connectivity requirement.
