jika titik titik (2,7), (6,-1), dan (9,m) terletak dalam satu garis lurus, maka nilai m adalah a. 3 b. 2 c. - 1 d. - 7 pakai caranya ya

A = (2,7)
B = (6,-1)
C = (9,m)

AB = (6,-1) - (2,7) = (4,-8)
BC = (9,m) - (6,-1) = (3,m + 1)

AB = k × BC
(4,-8) = k × (3,m + 1)
(4,-8) = (3k, k(m + 1))
4 = 3k
4/3 = k

k(m + 1) = -8
4/3(m + 1) = -8
4/3m + 4/3 = -8
4/3m = -28/3
m = -28/3 × 3/4
m = -7 (D)
maaf kalau salah..