a. 2PQ→−2PR→=⟨8,−4⟩2\overrightarrow{PQ} - 2\overrightarrow{PR} = \lang 8, -4\rang2PQ−2PR=⟨8,−4⟩; b. 2PQ→−2PR→=8i−4j2\overrightarrow{PQ} - 2\overrightarrow{PR} = 8\bold{i} - 4\bold{j}2PQ−2PR=8i−4j