Question Number 89268 by I want to learn more last updated on 16/Apr/20
$$\boldsymbol{\mathrm{Please}}\:\boldsymbol{\mathrm{help}}\:\boldsymbol{\mathrm{with}}\:\boldsymbol{\mathrm{this}}\:\boldsymbol{\mathrm{summation}}. \\ $$$$\:\:\:\underset{\boldsymbol{\mathrm{k}}\:\:=\:\:\mathrm{0}} {\overset{\boldsymbol{\mathrm{n}}} {\sum}}\left(−\:\mathrm{1}\right)^{\boldsymbol{\mathrm{k}}} \:\:\overset{\boldsymbol{\mathrm{n}}} {\:}\boldsymbol{\mathrm{C}}_{\boldsymbol{\mathrm{k}}} \:\boldsymbol{\mathrm{y}}_{\boldsymbol{\mathrm{n}}\:\:−\:\:\boldsymbol{\mathrm{k}}} \:\:\:\:=\:\:\:??? \\ $$