Solución

a. 2PQ2PR=8,42\overrightarrow{PQ} - 2\overrightarrow{PR} = \lang 8, -4\rang; b. 2PQ2PR=8i4j2\overrightarrow{PQ} - 2\overrightarrow{PR} = 8\bold{i} - 4\bold{j}