A cell phone plan has a monthly cost that is shown in the table below. What is the correct statement regarding the average rate of change during the 40-minute time of talk?

(-infinity,infinity)

answer: the value of b is 24 + 3t / (4- t ) = b

solution:

step 1 : find the slope using the formula below with the c (t, 3) and d(4, -3)

m = y2-y1 / x2 - x1

m = -3 -3 / 4-t

m = -6/4-t

to find the value of   b use the equation given in the question

note : use any of the pair given c or d in the equation to find the value of b i will be using d ( 4, -3)

y = mx+ b

3 = (-6/4-t)(4) + b don't forget to take the lcm

b = (36 - 3 t ) / ( 4 - t )

only 2 solutions are positive

also the part with what number should be added to both sides of the equation

should be 2 or 4