The line containing the points (1,a) and (3,b) has slope -2...

Question

The line containing the points (1,a) and (3,b) has slope -2. Find the slope of the line containing the points (1,-a) and (3,-b).

 

a. -2
b. -1/2
c. 1/2
d. 2
e. not unique

Answer 1

If the line contains the points (1,a) and (3,b), then the slope of the line is (b-a)/(3-1) = (b-a)/2 = -2.  So, b-a = -4

 

If a line contains the points (1,-a) and (3,-b), then the slope is             (-b-(-a))/(3-1) = (-b+a)/2

 

                     = -(b-a)/2 = -(-4)/2 = 2