Question

The set of points R(-1, 1), S(2, 4), T(6, 8) are collinear and the line has a slope of _____.

A.-1
B.1/2
C.1
D.-1/2

Answer 1

Slope= rise/run
         = change in y / change in x
         = y - y₂/ x-x₂

R(-1, 1), S(2, 4), T(6, 8) 

Using points S and T -------(x,y)
S: y=4, x=2
T: y₂=8, x₂=6

Then insert into 
Slope=y - y₂/ x-x₂
         = 4 - 8/ 2-6
         = -4/-4
         = 1

The slope is one

Answer 2

Answer:

OptionC

Step-by-step explanation:

Let the point R and S form a line.

The slope of line RS would be

Change in y coordinate/change in x coordinate

=$\frac{4-1}{2-(-1)} =1$

Now let us consider the line joining S and T

slope of line ST would be

=Change in y coordinate/change in x coordinate

=$\frac{8-4}{6-2)} =1$

Thus we find the slopes of RS and ST are equal

Since parallel lines will have equal slopes, here S is the common point

So RS and ST have to be the same line.

Or the three points are collinear with slope = 1