Suatu garis melalui titik ( m, -9 ) dan (7, m ) dengan kemiringan m. Berapa nilai m??

m = y2-y1/x2-x1= (-9-m)/(m-7)
m(m-7) = (-9-m)
m^2-7m = -9-m
m^2-6m +9 =0
(M-3)(m-3) =0
m = 3.