Question

question

Answer 1

\[\sum^∞_{k=1}(-1)^{k+2}=(-1)^{1+2}+(-1)^{2+2}+(-1)^{3+2}+(-1)^{4+2}+...\]\[~~~~~~~~~~~~~~~~~~~~=(-1)^{3}+(-1)^{4}+(-1)^{5}+(-1)^{6}+...\]\[~~~~~~~~~~~~~~~~~~~~=(-1)+1+(-1)+1+...\]