Step 1
Three points are collinear if the slope of any two pairs of points is the same.
With three points A, B, and C, three pairs of points can be formed, they are AB, BC, and AC. If Slope of AB = slope of BC = slope of AC, then A, B, and C are collinear points.
Step 2
DC and BA are colinear and therefore, will have the same slope.
[tex]\text{Slope}=\frac{rise}{\text{run}}[/tex]
For AB, the slope is given as;
[tex]\begin{gathered} \text{Rise}=1 \\ \text{Run}=2 \\ \text{Slope}=\frac{Rise}{Run}=\frac{1}{2} \end{gathered}[/tex]
For DC, the slope of BA=slope of DC since all 4 points are colinear.
[tex]\text{Slope of }\bar{\text{DC}}=\frac{1}{2}[/tex]
Answer; Slope of DC=1/2
