  A submanifold $M^n$ of a Euclidean space $\mathbb{E}^N$ is called biharmonic
if $\Delta\vec{H}=0$, where $\vec{H}$ is the mean curvature vector of $M^n$. A
well known conjecture of B.Y. Chen states that the only biharmonic submanifolds
of Euclidean spaces are the minimal ones. Ideal submanifolds were introduced by
Chen as those which receive the least possible tension at each point. In this
paper we prove that every $\delta(r)$-ideal biharmonic hypersurfaces in the
Euclidean space $\mathbb{E}^{n+1}$ ($n\geq 3$) is minimal. In this way we
generalize a recent result of B. Y. Chen and M. I. Munteanu. In particular, we
show that every $\delta(r)$-ideal biconservative hypersurface in Euclidean
space $\mathbb{E}^{n+1}$ for $n\geq 3$ must be of constant mean curvature.
