Question

On a very cold morning, it was -8°F. As the day went on, the temperature rose 2 degrees each hour. Which equation shows the temperature over time?

A. y = -2x + 8
B. y = -2x – 8
C. y = 2x + 8
D. y = 2x – 8

Answer 1

If we read this problem carefully, it becomes obvious that there's an initial temperature (vertical intercept) of -8 degrees F, and that there's also an hourly increase in the temperature. Thus, the slope-intercept model is called for:

y = mx + b. m is the slope and in this problem is +2 degrees F per hour, and b is the y-intercept, -8 degrees F. The variable x represents the number of hours that have passed since the first (-8 degree) measurement was taken:

T(x) = -8 degrees F + (+2 degrees F per hour)(x), where x is measured in hours.

The best fit to this is the fourth answer choice, y = 2x-8.

Answer 2

I believe your answer to this, would have to be D. y=2x-8, because since it changes 2 degrees each hour, and the degrees is at -8 degrees that morning, I would presume that it would still be cold. So, the answer would be y=2x-8 showing 2x - (-8).