The credit remaining on a phone card (in dollars) is a linear function of the total calling time made with the card (in minutes). The remaining credit after 43 minutes of call is $19.84, and the remaining credit after 65 minutes of call is $17.20. What is the remaining credit after 79 minutes of call.

the remaining credit after 79 minutes of call is $15.52

Step-by-step explanation:

let x represent the number of minutes of call.

Let y represent the remaining credit after x minutes of call.

If we plot y on the vertical axis and x on the horizontal axis, a straight line would be formed. The slope of the straight line would be

Slope, m = (17.2 - 19.84)/(65 - 43)

m = - 2.64/22 = - 0.12

The equation of the straight line can be represented in the slope-intercept form, y = mx + c

Where

c = intercept

m = slope

To determine the intercept, we would substitute x = 65, y = 17.2 and m = - 0.12 into y = mx + c. It becomes

17.2 = - 0.12 × 65 + c

17.2 = - 7.8 + c

c = 17.2 + 7.8

c = 25

The linear function becomes

y = - 0.12x + 25

Therefore, the remaining credit after 79 minutes of call is

y = - 0.12 × 79 + 25

y = - 9.4 + 25

y = 15.52

explanation:

previous steps have made pa≅ pb ≅ st ≅ su. setting the compass width to ab allows you to make tu the same length. then δstu ≅ δpab by the sss congruence postulate, and ∠p ≅ ∠s by the reason cpctc.

answer: cos [   arcsin (3/5) - arccos (1/2) ] =

step-by-step explanation: × = 3/5 = 0.6--> x = 36.87 and x = 180 - 36.87 = 143.13 deg

cos y = 1/2 --> y = +- 60 deg a. cos (x - y) = cos (143.13 - 60) = cos 83,13  

=

0.12

b. cos (36.87 - 60) = cos (-23.23) = 0.92