We denote by $\mathcal { C }$ the vector space of continuous functions from $[ 0,1 ]$ to $\mathbb { R }$, equipped with the supremum norm $\| f \| _ { \infty } = \sup _ { x \in [ 0,1 ] } | f ( x ) |$. For $f \in \mathcal { C }$ and $n \in \mathbb { N } ^ { * }$, the $n$-th Bernstein polynomial of $f$ is defined by $$B _ { n } ( f ) ( x ) = \sum _ { k = 0 } ^ { n } f \left( \frac { k } { n } \right) \binom { n } { k } x ^ { k } ( 1 - x ) ^ { n - k }$$ for all $x \in [ 0,1 ]$. Let $f \in \mathcal { C }$. Show, for all $x \in [ 0,1 ]$, the relation $$B _ { n } ( f ) ( x ) - f ( x ) = \sum _ { k = 0 } ^ { n } \left( f \left( \frac { k } { n } \right) - f ( x ) \right) \binom { n } { k } x ^ { k } ( 1 - x ) ^ { n - k }$$
We denote by $\mathcal { C }$ the vector space of continuous functions from $[ 0,1 ]$ to $\mathbb { R }$, equipped with the supremum norm $\| f \| _ { \infty } = \sup _ { x \in [ 0,1 ] } | f ( x ) |$. For $f \in \mathcal { C }$ and $n \in \mathbb { N } ^ { * }$, the $n$-th Bernstein polynomial of $f$ is defined by
$$B _ { n } ( f ) ( x ) = \sum _ { k = 0 } ^ { n } f \left( \frac { k } { n } \right) \binom { n } { k } x ^ { k } ( 1 - x ) ^ { n - k }$$
for all $x \in [ 0,1 ]$.
Let $f \in \mathcal { C }$. Show, for all $x \in [ 0,1 ]$, the relation
$$B _ { n } ( f ) ( x ) - f ( x ) = \sum _ { k = 0 } ^ { n } \left( f \left( \frac { k } { n } \right) - f ( x ) \right) \binom { n } { k } x ^ { k } ( 1 - x ) ^ { n - k }$$