Let
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be the algebra of all
n×n upper triangular matrices. We say that an element
2448674f500d553adec1627a11"">![]()
is an all-derivable point of
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if every derivable linear mapping
φ at
G (i.e.
φ(ST)=φ(S)T+Sφ(T) for any
![]()
with
ST=G) is a derivation. In this paper we show that
![]()
is an all derivable point of
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if and only if
G≠0.