Linea ab pases through points a (-6,7) and b(-6,-3) as shown on the coordinate grid below

x= -6

Step-by-step explanation:

Notice that a(-6,7) and b(-6,-3) have the same x-coordinate (-6).  This means that x is constant and that the line is a vertical one (x = -6).

The equation of the line through these two points is x = -6.  

step-by-step explanation:

- "runner b is moving at a slower rate."

- "the graphs shown are graphs of distance(km) against time(min).

the slopes of this graphs are are given by:

slope = (change in y)/(change in x)

= (change in distance)/(change in time)

this is the formula for finding the speed. so, the slope of these graphs represent the speed of the runner.

taking each division in the graph to represent 1 on both axis:

runner a ⇒ speed = (2-0)/(1-0)

= 2/1

= 2 km/min

runner b ⇒ speed = (3-0)/(3-0)

= 3/3

= 1 km/min

this shows that   runner b is moving at a slower rate."