Problem: The points (2,β3),(4,3) and (5,2kβ) are on the same straight line. The value(s) of k is (are):
Answer Choices:
A. 12
B. β12
C. Β±12
D. 12 or 6
E. 6 or 632β
Solution:
m=ΞxΞyβ=4β23+3β=5β4k/2β3βk=12
where Ξy=y2ββy1β, etc.