Which expression is not equivalent to the other three?

-9 - 7n + 16n

9(n - 9)

n - 9 + 8n

9n - 9

9(n - 9)  = 9n - 81

Step-by-step explanation:

Equivalent expressions are expressions which are equal . To determine if expressions are equivalent, simplify to lowest terms through combining like terms.

-9 - 7n + 16n  =  -9 + 9n

9(n - 9)  = 9n - 81

n - 9 + 8n  = -9 + 9n

9n - 9 = -9 + 9n

- "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."