1. 4) PM
2. 3) OA = OC, 6) AB=DC
3. $$3\vec{n} = 3 \cdot (-3; 4) = (-9; 12)$$ $$-4\vec{k} = -4 \cdot (1; 2) = (-4; -8)$$ $$\vec{b} = 3\vec{n} - 4\vec{k} = (-9; 12) + (-4; -8) = (-13; 4)$$ 2) {-13; 4}