Answer:
A
Step-by-step explanation:
Since they lie on the same line, it means that they are collinear.
Since they are collinear, the value of the slope between each 2 point is the same. Hence, we can have points PQR with the slopes PQ, PR and QR being the same.
The general formula for finding the slope of a line with 2 end points is :
m = (y2 - y1)/(x2 - x1)
using the first two points,
m = (0 - 9)/-1 -2 = -9/-3 = 3
Now to get the value of n. We can use the second point and the point containing n.
This means:
3 = (21 - 0)/(n + 1)
3 = 21/n + 1
3n + 3 = 21
3n = 18
n = 6
