Select the correct answer from each drop-down menu. ∆abc has the points a(1, 7), b(-2, 2), and c(4, 2) as its vertices. the measure of the longest side of ∆abc is units. ∆abc is triangle. if ∆abd is formed with the point d(1, 2) as its third vertex, then ∆abd is triangle. the length of side ad is units.