It is proved that, if f (x) is an element of L-[-1,1](p), < p < infinity, changes sign exactly l times, then there exists a real rational function r(x) is an element of R-n(l) such that parallel to f-r parallel to(p) <= C-p,C-delta(l + 1)(2) omega(f, (n-1))(p), which generalizes a result of Leviatan and Lubinsky in [2]. A weaker similar result in L-[-1,1](1) is also established.
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Moscow MV Lomonosov State Univ, Fac Mech & Math, Moscow 119992, RussiaMoscow MV Lomonosov State Univ, Fac Mech & Math, Moscow 119992, Russia
Alimov, A. R.
Tsar'kov, I. G.
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Moscow MV Lomonosov State Univ, Fac Mech & Math, Moscow 119992, Russia
Moscow Ctr Fundamental & Appl Math, Moscow, RussiaMoscow MV Lomonosov State Univ, Fac Mech & Math, Moscow 119992, Russia