  A study of three-pseudoscalar $\pi K \bar{K}$ and $\pi \pi \eta$ coupled
system is made by solving the Faddeev equations within an approach based on
unitary chiral dynamics. A resonance with total isospin one and spin-parity
$J^\pi = 0^-$ is found with mass $\sim$ 1400 MeV when the $K \bar{K}$ system
gets reorganized as the $f_0(980)$. This resonance is identified with the $\pi
(1300)$ listed by the Particle Data Group. Further, the two-body amplitude
which describes the interaction between a $\pi$ and the $f_0(980)$ is extracted
from the study of the $\pi K\bar K$ and $\pi\pi\eta$ system and is then
employed to study the $f_0(980)\pi \pi $ system. As a result, a scalar
resonance is found near 1790 MeV which drives the two $ f_0 (980)\pi$ systems
to resonate as the $\pi (1300)$ while the invariant mass of the two pions falls
in the mass region of the scalar $\sigma (600)$. These findings support the
existence of a new $f_0$ resonance near 1790 MeV, as found by the BES and
Crystal Barrel collaborations. Our results show that this $f_0(1790)$ is
definitely distinct to $f_0(1710)$, the latter of which seems to possess a
glueball structure dominantly.
