Let $a,b \in \mathbb{R}$ satisfy $a < b$, let $n \in \mathbb{N}$, and let $X \subset C([a,b];\mathbb{R})$ be an $n$-dimensional Haar space, meaning that every nonzero function $h \in X$ has at most $n-1$ distinct zeros in $[a,b]$. Let $f \in C([a,b];\mathbb{R})$ and $p \in X$. Define
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\begin{align*}
E := \|f-p\|_{C([a,b])} = \max_{x \in [a,b]} |f(x)-p(x)|.
\end{align*}
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Then $p$ is a best uniform approximation to $f$ from $X$, that is,