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Pietro Majer
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Consider, for $m\ge2$, the function $\varphi_m(x):=x(1-x)^m$ . So $$\varphi_m(0)=0\qquad \varphi_m(1)=0$$ $$ \varphi_m'(0)=1\qquad \varphi_m'(1)=0\ .$$ It is also easy to see that $\| \varphi_m'\|_2=O(m^{-{1/2}})$ (in fact, we may compute exactly both $\| \varphi_m\|_2^2$ and $\| \varphi_m'\|_2^2$ in terms of some rational functions of $m$, by means of a few Beta function integrals).

For any $v\in H^2(0,1)$ define

$$v_m(x):=v(x)-v(0)\varphi_m(x)-v(1)\varphi_m(1-x)$$

then clearly $v_m\in V$ and $\|v-v_m\|_{1,2}=O(m^{-{1/2}})$.

Pietro Majer
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