Problem: The points (2,−3),(4,3) and (5,2k​) are on the same straight line. The value(s) of k is (are):
Answer Choices:
A. 12
B. −12
C. ±12
D. 12 or 6
E. 6 or 632​
Solution:
m=ΔxΔy​=4−23+3​=5−4k/2−3​k=12
where Δy=y2​−y1​, etc.