1. **Problem statement:** Find the length of line segment PQ where P(-1,1) and Q(3,4). 2. **Formula used:** The distance between two points $P(x_1,y_1)$ and $Q(x_2,y_2)$ is given by: $$d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$$ 3. **Calculate the differences:** $$x_2 - x_1 = 3 - (-1) = 4$$ $$y_2 - y_1 = 4 - 1 = 3$$ 4. **Calculate the distance:** $$d = \sqrt{4^2 + 3^2} = \sqrt{16 + 9} = \sqrt{25} = 5$$ **Final answer:** The length of line PQ is 5 units.