I am stuck in a small problem. I am trying to prove that for all $x,y \in l^{2}(\mathbb{R})$, it holds that: $\left\langle\left(\downarrow M\right)\left[x\right],y \right\rangle = \left\langle x,\left(\uparrow M\right)\left[y\right] \right\rangle $.$$\left\langle\left(\downarrow M\right)\left[x\right],y \right\rangle = \left\langle x,\left(\uparrow M\right)\left[y\right] \right\rangle \text{.}$$ How should I proceed to prove this. Any help or ideas.
Thanks.?